pyjwt

Claims validation

Claims Validation in JWT

What are Claims?

Claims are pieces of information that are included in a JWT. They can be anything, but they typically include information about the user, the token's expiration date, and the issuer of the token.

Validating Claims

When you receive a JWT, you need to validate its claims to make sure they are genuine. This involves:

Checking the signature: The signature is a digital fingerprint of the JWT that is created using a cryptographic key. You can use the public key of the issuer to verify the signature.
Checking the expiration date: The expiration date is a timestamp that indicates when the JWT expires. You should check that the current date is before the expiration date.
Checking the issuer: The issuer is the entity that created the JWT. You should check that the issuer is who you expect it to be.

Real-World Implementations

Here's a Python example of how to validate claims in a JWT:

import jwt

token = jwt.decode(jwt_string, public_key)

if token['exp'] <= datetime.now():
    raise ValueError('JWT expired.')

if token['iss'] != 'issuer':
    raise ValueError('JWT is not from the correct issuer.')

Applications

Claims validation is essential for securing applications that use JWTs. It helps to prevent:

Token forgery: Attackers could create fake JWTs that appear to be from a trusted issuer.
Token replay: Attackers could replay old JWTs that have expired to gain unauthorized access.
Man-in-the-middle attacks: Attackers could intercept JWTs and modify the claims before they reach the intended recipient.

Claims

What are JWT Claims?

A JWT (JSON Web Token) is made up of three parts: the header, the payload, and the signature. The payload is where claims are stored. Claims are statements about the identity of the subject of the token and other relevant information.

Types of Claims

There are three main types of claims:

Registered claims: These are claims that have standardized names and values. They include things like the issuer, subject, and expiration time of the token.
Public claims: These are claims that can be defined by the application that creates the token. They can be used to store any information that is relevant to the application.
Private claims: These are claims that are only recognized by the parties that create and consume the token. They can be used to store sensitive information that should not be shared with others.

Issuing Claims

Claims are issued by the token creator. The creator can use any combination of registered, public, and private claims. When creating a token, the creator must specify the values of the claims.

Using Claims

Claims are used by the token consumer. The consumer can use the values of the claims to make decisions about the token. For example, the consumer can use the expiration time claim to determine if the token is still valid.

Real-World Examples

JWTs are used in a wide variety of applications, including:

Authentication: JWTs can be used to authenticate users to applications. The JWT can contain claims about the user's identity, such as their username and email address.
Authorization: JWTs can be used to authorize users to access resources. The JWT can contain claims that specify the user's permissions.
Data exchange: JWTs can be used to exchange data between applications. The JWT can contain claims that represent the data being exchanged.

Simplified Explanation

Imagine a JWT as a letter. The header is like the envelope, the payload is like the letter itself, and the signature is like the wax seal. The payload can contain any information you want, but there are some common things that are included, like the name of the person who wrote the letter, the date it was written, and the message.

Complete Code Implementation

Here is an example of how to create a JWT with claims:

import jwt

claims = {
    "iss": "your-issuer-name",
    "sub": "your-subject-name",
    "exp": 1577836800,
    "custom_claim": "your-custom-claim-value"
}

token = jwt.encode(claims, "your-secret-key")

Here is an example of how to decode a JWT and access the claims:

import jwt

token = "your-encoded-token"
claims = jwt.decode(token, "your-secret-key")

print(claims["iss"])
print(claims["sub"])
print(claims["exp"])
print(claims["custom_claim"])

Key rotation

Key Rotation in JWT

Key Rotation is a security measure that involves changing the cryptographic key used to sign and verify JWTs. This is done to reduce the risk of a compromised key being used to forge or compromise tokens.

How Key Rotation Works

Key rotation involves the following steps:

Generate a new key pair: Create a new public-private key pair to be used for signing and verifying JWTs.
Update the signing key: Replace the old signing key with the new one. This means any new JWTs will be signed with the new key.
Distribute the new public key: Share the new public key with any parties who need to verify JWTs. This allows them to update their systems to use the new key.
Expire the old key: Set an expiration date for the old key, after which it will no longer be valid for signing or verifying JWTs.

Benefits of Key Rotation

Improved security: Reduces the risk of compromised keys being used to forge tokens.
Compliance with industry standards: Many security regulations require regular key rotation to ensure the confidentiality and integrity of data.
Increased confidence in JWTs: Key rotation helps to maintain trust in the use of JWTs for authorization and data exchange.

Real-World Applications

Key rotation is used in various applications, including:

Financial transactions: To protect sensitive financial data from unauthorized access.
Healthcare systems: To safeguard patient health records.
E-commerce platforms: To secure online purchases.

Code Implementation

Here's a simplified code example for key rotation using PyJWT:

import jwt

# Generate a new key pair
private_key, public_key = jwt.generate_keypair()

# Sign a JWT with the new key
token = jwt.encode(
    {"data": "my_secret_data"},
    private_key,
    algorithm="HS256",
)

# Verify the JWT with the new key
decoded_token = jwt.decode(
    token,
    public_key,
    algorithms=["HS256"],
)

# Expire the old key after 1 hour
old_key_expiration_date = datetime.datetime.now(tz=datetime.timezone.utc) + datetime.timedelta(hours=1)

Summary

Key rotation is a critical security measure for protecting the integrity and confidentiality of JWTs. It involves regularly changing the cryptographic key used for signing and verifying tokens, reducing the risk of compromised keys being exploited.

Stateful authentication

Simplified Explanation

Stateful Authentication uses a server to store information about the user's session. Every time the user makes a request to log in or access a protected resource, the server checks if the user is already logged in and has a valid session. If so, the server grants access. Otherwise, the user needs to log in again.

Important Concepts

Session: A unique identifier associated with a user's logged-in state. The server stores the session in a database or cache.

Session Token: A cookie or header value that the user presents with each request to identify their session.

Identity Provider (IdP): A third-party service that handles user authentication and provides session tokens.

Real-World Example

A typical example of stateful authentication is a website that uses cookies to keep track of users' sessions. When a user logs in, the server creates a session for them and stores a cookie on their device. The cookie contains a session token that the user sends back with every subsequent request. The server checks the session token to verify that the user is still logged in and grants access accordingly.

Potential Applications

Stateful authentication is widely used in web applications, e-commerce platforms, and online banking systems where:

Maintaining a logged-in state is crucial for the user experience.
Protecting sensitive resources and preventing unauthorized access is essential.

Simplified Code Example

Server-side:

from flask import Flask, request

app = Flask(__name__)

sessions = {}

@app.route('/login')
def login():
    username = request.form['username']
    password = request.form['password']
    if username == 'admin' and password == 'secret':
        session_id = str(uuid4())
        sessions[session_id] = username
        return jsonify({'session_id': session_id})
    return jsonify({'error': 'Invalid credentials'})

@app.route('/protected')
def protected():
    session_id = request.headers.get('Session-Id')
    if session_id not in sessions:
        return jsonify({'error': 'Unauthorized'})
    return jsonify({'message': 'Protected resource accessible'})

Client-side:

// Login
fetch('/login', {
  method: 'POST',
  body: JSON.stringify({
    username: 'admin',
    password: 'secret'
  })
})
  .then(res => res.json())
  .then(data => {
    // Store the session ID in a cookie
    document.cookie = `session_id=${data.session_id}; path=/`;
  });

// Access protected resource
fetch('/protected', {
  headers: {
    'Session-Id': document.cookie.split('=')[1]
  }
})
  .then(res => res.json())
  .then(data => {
    // Display the protected resource
    console.log(data.message);
  });

Token payload

Token Payload

Imagine a secret message inside a locked box (the token). The payload is the message itself, containing information that you want to share securely.

Components:

Claims: Key-value pairs that hold specific information, like:
- iss: Issuer (who created the token)
- sub: Subject (who the token is for)
- exp: Expiration time (when the token becomes invalid)
Custom Claims: Additional information you can include, like user preferences or permissions

Creating a Payload with Claims:

import jwt

claims = {
    'iss': 'Your-issuer-name',
    'sub': 'Your-subject-name',
    'exp': datetime.now() + timedelta(minutes=15)
}

token = jwt.encode(claims, 'your-secret-key')

Decoding a Payload:

import jwt

decoded_token = jwt.decode(token, 'your-secret-key')

print(decoded_token['iss'])  # Output: 'Your-issuer-name'

Applications:

Authentication: Verifying user identity in online services
Authorization: Granting access to specific resources based on payload claims
Data sharing: Securely exchanging information between different parties

Token tampering prevention

Token Tampering Prevention

When you create a token, you want to make sure that it can't be tampered with. This means that someone can't change the data in the token without you knowing about it.

Two steps you can take to prevent token tampering are:

Use a Signature

A signature is like a digital fingerprint. It's a unique identifier that's generated based on the data in the token.

When a token is created, a signature is added to the end of the token. When someone tries to read the token, the signature is checked to make sure that it matches the data in the token. If the signature doesn't match, that means the token has been tampered with.

import jwt

# Create a secret key
secret_key = "secret-key"

# Create a token
token = jwt.encode({"foo": "bar"}, secret_key, algorithm="HS256")

# Decode the token
decoded_token = jwt.decode(token, secret_key, algorithms=["HS256"])

# Check the signature
print(decoded_token["foo"] == "bar")  # True

Use a Header

The header tells the reader that information about how the token is encoded. This includes the algorithm that was used to sign the token.

If someone tries to change the data in the token, they'll also need to change the header. However, if they don't know the algorithm that was used to sign the token, they won't be able to do this.

import jwt

# Create a header
header = {"alg": "HS256"}

# Create a token
token = jwt.encode({"foo": "bar"}, "secret-key", header=header)

# Decode the token
decoded_token = jwt.decode(token, "secret-key", algorithms=["HS256"])

# Check the header
print(decoded_token["foo"] == "bar")  # True
print(decoded_token["header"]["alg"] == "HS256")  # True

Real World Applications

Token tampering prevention is used in many applications where it's important to ensure that data is not tampered with. For example, it's used in:

Authentication: To ensure that users are who they say they are
Authorization: To ensure that users have the permission to access certain resources
Data integrity: To ensure that data has not been changed without authorization

Error handling

Error Handling in JWT

1. InvalidTokenError

Occurs when the token is malformed or invalid.
Can be caused by:
- Invalid signature
- Expired token
- Token has not yet been activated
Example:

try:
    payload = jwt.decode(token, key, algorithms=["HS256"])
except jwt.InvalidTokenError:
    print("Invalid token!")

2. DecodeError

Occurs when the token cannot be decoded.
Can be caused by:
- Invalid encoding
- Unsupported algorithm
Example:

try:
    payload = jwt.decode(token, key, algorithms=["HS256"])
except jwt.DecodeError:
    print("Could not decode token!")

3. ExpiredSignatureError

Occurs when the token has expired.
Can be caused by:
- Token has a defined expiration time
- Clock skew (difference between the token issuer's and receiver's clocks)
Example:

try:
    payload = jwt.decode(token, key, algorithms=["HS256"], options={"verify_exp": True})
except jwt.ExpiredSignatureError:
    print("Token has expired!")

4. InvalidAlgorithmError

Occurs when the algorithm used to sign the token is not supported.
Can be caused by:
- Incorrect algorithm specified in the function call
- Unsupported algorithm
Example:

try:
    payload = jwt.decode(token, key, algorithms=["HS256"])
except jwt.InvalidAlgorithmError:
    print("Unsupported algorithm!")

5. InvalidIssuedAtError

Occurs when the token's "iat" (issued at) claim is not a valid date.
Can be caused by:
- Invalid timestamp
- Clock skew
Example:

try:
    payload = jwt.decode(token, key, algorithms=["HS256"], options={"verify_iat": True})
except jwt.InvalidIssuedAtError:
    print("Invalid issued at timestamp!")

6. InvalidExpiresAtError

Occurs when the token's "exp" (expires at) claim is not a valid date.
Can be caused by:
- Invalid timestamp
- Clock skew
Example:

try:
    payload = jwt.decode(token, key, algorithms=["HS256"], options={"verify_exp": True})
except jwt.InvalidExpiresAtError:
    print("Invalid expires at timestamp!")

7. InvalidAudienceError

Occurs when the token's "aud" (audience) claim does not match the expected audience.
Can be caused by:
- Incorrect audience specified in the function call
- Token intended for a different audience
Example:

try:
    payload = jwt.decode(token, key, algorithms=["HS256"], audience="example.com")
except jwt.InvalidAudienceError:
    print("Invalid audience!")

8. InvalidIssuerError

Occurs when the token's "iss" (issuer) claim does not match the expected issuer.
Can be caused by:
- Incorrect issuer specified in the function call
- Token issued by a different issuer
Example:

try:
    payload = jwt.decode(token, key, algorithms=["HS256"], issuer="example.com")
except jwt.InvalidIssuerError:
    print("Invalid issuer!")

Real-World Applications:

Authentication: Verifying user identity and authorization.
Authorization: Granting or denying access to resources.
Data Exchange: Securely sharing data between parties.
API Security: Protecting API endpoints from unauthorized access.
Device Management: Provisioning and managing IoT devices.

Use cases and examples

Use Cases and Examples

Use Case 1: Authenticating Users

Concept: When a user logs in to a website or app, a JWT is created and sent back to the user. This JWT contains information about the user, such as their username and permissions. When the user accesses a protected part of the website or app, the JWT is sent along with the request. The server can then verify the JWT to ensure that the user is authorized to access the resource.

Example:

# Generate a JWT
import jwt
import datetime

payload = {
    "iss": "your_website_url",
    "sub": "username",
    "iat": datetime.datetime.utcnow(),
    "exp": datetime.datetime.utcnow() + datetime.timedelta(hours=1),
}

token = jwt.encode(payload, "your_secret_key")

# Verify a JWT
import jwt
from time import time

token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJ5b3VyX3dlYnNpdGVfdXJsIiwic3ViIjoiVXNlcm5hbWUiLCJpYXQiOjE2NTg0NTQ4MzMsImV4cCI6MTY1ODQ1ODQzM30.nZ_Olv6b8y4t5bnyuX1w_279d4L5-p79d1yI-GQmHb0"

try:
    decoded_token = jwt.decode(token, "your_secret_key", algorithms=["HS256"])
except jwt.ExpiredSignatureError:
    print("Token expired. Please log in again.")
except jwt.InvalidTokenError:
    print("Invalid token. Please try again.")
else:
    print("Token is valid.")

Potential Applications:

Websites and apps
APIs
Mobile apps

Use Case 2: Data Transfer

Concept: JWTs can be used to securely transfer data between two parties. For example, a company might use a JWT to share confidential information with a partner company. The JWT would contain the data, as well as a signature that ensures that the data has not been tampered with.

Example:

# Generate a JWT with data
import jwt
import datetime

payload = {
    "data": "Your confidential data",
    "iat": datetime.datetime.utcnow(),
    "exp": datetime.datetime.utcnow() + datetime.timedelta(hours=1),
}

token = jwt.encode(payload, "your_secret_key")

# Verify a JWT with data
import jwt
from time import time

token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJkYXRhIjoiWW91ciBjb25maWRlbnRpYWwgZGF0YSIsImlhdCI6MTY1ODQ1NDgzMywiZXhwIjoxNjU4NDU4NDMzfQ.nZ_Olv6b8y4t5bnyuX1w_279d4L5-p79d1yI-GQmHb0"

try:
    decoded_token = jwt.decode(token, "your_secret_key", algorithms=["HS256"])
    print("Data:", decoded_token["data"])
except jwt.ExpiredSignatureError:
    print("Token expired. Please try again.")
except jwt.InvalidTokenError:
    print("Invalid token. Please try again.")
else:
    print("Token is valid.")

Potential Applications:

Secure data sharing between companies
Data exchange between different systems
Transfer of sensitive information

Use Case 3: Tracking User Activity

Concept: JWTs can be used to track user activity on a website or app. For example, a website might use a JWT to store information about a user's recent purchases or page views. This information can be used to personalize the user's experience or to track user behavior for analytics purposes.

Example:

# Generate a JWT with user activity data
import jwt
import datetime

payload = {
    "user_id": "123",
    "activities": [
        {"page_viewed": "Home Page", "time": datetime.datetime.utcnow()},
        {"item_purchased": "T-Shirt", "time": datetime.datetime.utcnow()},
    ],
    "iat": datetime.datetime.utcnow(),
    "exp": datetime.datetime.utcnow() + datetime.timedelta(hours=1),
}

token = jwt.encode(payload, "your_secret_key")

# Verify a JWT with user activity data
import jwt
from time import time

token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyX2lkIjoiMTIzIiwibmFtZSI6IlVzZXIgTmFtZSIsImVtYWlsIjoidXNlckBleWFtcGxlLmNvbSIsInJvbGVzIjpbInVzZXIiXSwiaWF0IjoxNjU4NDU0ODMzLCJleHAiOjE2NTg0NTg0MzN9.nZ_Olv6b8y4t5bnyuX1w_279d4L5-p79d1yI-GQmHb0"

try:
    decoded_token = jwt.decode(token, "your_secret_key", algorithms=["HS256"])
    print("User activities:", decoded_token["activities"])
except jwt.ExpiredSignatureError:
    print("Token expired. Please try again.")
except jwt.InvalidTokenError:
    print("Invalid token. Please try again.")
else:
    print("Token is valid.")

Potential Applications:

Tracking user behavior for analytics purposes
Personalizing user experiences
Improving user engagement

OAuth 2.0

OAuth 2.0 in a Nutshell

Imagine you have a vault with your precious secrets, and you want to give someone access to a specific secret without actually handing them the key. That's where OAuth 2.0 comes in!

Authorization Server: Think of this as the vault keeper. It holds the secrets and grants access to them.

Resource Server: This is your vault where the secrets are stored.

Client: The person who wants access to a specific secret.

OAuth 2.0 Flow

1. Client Requests Access: The client asks the authorization server for a "token" that will grant access to a specific secret.

2. Authorization Server Checks Client: The server checks if the client is authorized to view the secret. If yes, it generates a token.

3. Server Returns Access Token: The token is sent back to the client.

4. Client Requests Resource: The client sends the token to the resource server, along with a request to access the secret.

5. Resource Server Verifies Token: The server checks if the token is valid and allows the client to view the secret.

Code Example

Authorization Server (Python):

from oauth2 import AuthorizationServer

# Create authorization server
server = AuthorizationServer()

# Client requests access token
client_id = 'my_client'
secret = 'my_secret'
scope = 'my_resource'
access_token = server.get_access_token(client_id, secret, scope)

# Print access token
print("Access token:", access_token)

Resource Server (Python):

from oauth2 import ResourceServer

# Create resource server
server = ResourceServer()

# Verify access token
access_token = 'my_access_token'
resource_id = 'my_resource'
valid = server.verify_access_token(access_token, resource_id)

# Grant access to resource
if valid:
    print("Access granted to resource:", resource_id)
else:
    print("Access denied")

Real-World Applications

Social Media Logins:
- OAuth 2.0 allows you to log into websites and apps using your social media accounts.
API Access:
- Businesses grant third-party developers access to their APIs using OAuth 2.0.
Mobile App Authentication:
- OAuth 2.0 can be used for authenticating mobile apps.

Revocation

Revocation

Concept: Revocation is a way to invalidate an existing JWT before its expiration date. This is useful when the token needs to be deactivated, such as if the user's password was changed or the token was compromised.

Process: To revoke a JWT, a revocation list (e.g., a database) is maintained that stores all the invalidated tokens. When a JWT is presented, it is checked against the revocation list before being accepted. If the token is on the list, it is considered invalid and rejected.

Implementation:

1. Create a Revocation List: Maintain a database table or in-memory dictionary to store invalidated tokens.

Database Table Example:

CREATE TABLE revoked_tokens (
  token_id TEXT PRIMARY KEY,
  revoked_at DATETIME NOT NULL
);

2. Revoke a Token: Add the token ID to the revocation list with the current timestamp.

Python Example:

import datetime

# Assuming you have a list of token IDs to revoke
for token_id in token_ids:
    revoked_tokens_db.insert({
        "token_id": token_id,
        "revoked_at": datetime.datetime.now()
    })

3. Check for Revocation: When a JWT is presented, query the revocation list to check if the token has been invalidated.

Python Example:

def is_revoked(token):
    token_id = token.decode("utf8")
    return revoked_tokens_db.get(token_id) is not None

Real-World Applications:

Authentication: Revoke tokens when users change passwords or are deactivated.
Authorization: Revoke tokens for specific roles or permissions.
Fraud Prevention: Revoke tokens suspected of being compromised.
Caching: Invalidate JWTs stored in local caches to ensure validity.

Community support

Community Support

What is Community Support?

Community support is a way for people to help each other solve problems and learn new things. It's like having a group of friends who can answer your questions, give you advice, and help you troubleshoot issues.

How Does Community Support Work in pyjwt?

The pyjwt community has a few different ways to provide support:

Documentation: The pyjwt documentation is a great resource for learning how to use the library. It covers everything from installation to advanced usage.
GitHub Issues: You can create a GitHub issue to report a bug, ask a question, or request a new feature. The pyjwt community will respond to your issue and try to help you resolve it.
Stack Overflow: You can ask questions about pyjwt on Stack Overflow. The pyjwt community will often answer these questions and help you find solutions.

How Can I Get Involved in Community Support?

There are a few ways to get involved in community support for pyjwt:

Answer questions on Stack Overflow: If you see a question about pyjwt that you can answer, please do so! This is a great way to help others and contribute to the community.
Report bugs: If you find a bug in pyjwt, please report it on GitHub. This will help the developers fix the bug and improve the library.
Request new features: If you have an idea for a new feature that you think would be useful, please create a GitHub issue. The developers will consider your request and may implement it in a future release.

Real-World Examples of Community Support

Here are a few examples of how community support has helped people use pyjwt:

A developer was having trouble getting pyjwt to work with their application. They asked a question on Stack Overflow and received several helpful responses from the pyjwt community.
A user found a bug in pyjwt and reported it on GitHub. The developers fixed the bug and released a new version of the library.
A user requested a new feature for pyjwt. The developers considered the request and implemented the feature in a future release.

Potential Applications in the Real World

Community support can be used in a variety of real-world applications, such as:

Software development: Community support can help developers troubleshoot issues, learn new techniques, and stay up-to-date on the latest changes in a software library.
Education: Community support can help students learn new concepts, get help with assignments, and connect with other learners.
Customer service: Community support can help customers resolve issues with a product or service, get answers to their questions, and learn how to use a product or service more effectively.

Key management

Key Management in PyJWT

What is Key Management?

Imagine you have a secret treasure chest. To protect your treasure, you need a key. Key management is all about handling that key securely so that only you can open the chest.

In the case of PyJWT, the key is used to sign and verify JWT tokens. A signed JWT proves that it came from a trusted source and hasn't been tampered with.

Types of Keys

There are two types of keys in PyJWT:

Symmetric Keys: These keys are the same for encryption and decryption. It's like having one key for both your front and back door.
Asymmetric Keys: These keys come in pairs: a private key and a public key. The private key is used for signing, while the public key is used for verifying. This is like having a key for your house and a different key for your car.

Key Generation

PyJWT provides functions to generate both symmetric and asymmetric keys:

# Generate a symmetric key
key = jwt.generate_symmetric_key()

# Generate an asymmetric key pair
private_key, public_key = jwt.generate_rsa_key()

Key Storage

Once you have a key, you need to store it securely. There are several ways to do this:

Environment Variables: Store the key in an environment variable that's only accessible to your application.
Configuration Files: Create a configuration file that contains the key.
In-Memory: Store the key in a secure location in your application's memory.

Real-World Applications

Key management is essential for any application that uses JWTs. For example:

Authentication: Use JWTs to authenticate users without storing their passwords.
Authorization: Use JWTs to grant access to different parts of your application.
Data Exchange: Use JWTs to securely exchange data between different systems.

Example Code

Here's an example of how to use symmetric key management to sign and verify a JWT:

import jwt

# Generate a symmetric key
key = jwt.generate_symmetric_key()

# Create a JWT using the key
token = jwt.encode({"username": "alice"}, key, algorithm="HS256")

# Verify the JWT using the key
decoded_token = jwt.decode(token, key, algorithms=["HS256"])

# Print the decoded payload
print(decoded_token)

Performance optimization

Performance Optimization

1. Use the Faster Algorithm

PyJWT supports two algorithms: HS256 and RS256.
HS256 is faster than RS256.
If security is not a concern, use HS256 for better performance.

Example:

import jwt

# Faster algorithm
token = jwt.encode({'data': 'my_data'}, 'secret', algorithm='HS256')

# Slower algorithm
token = jwt.encode({'data': 'my_data'}, 'secret', algorithm='RS256')

2. Disable Verification

Verification ensures the integrity of the JWT.
It is computationally expensive.
If you trust the source of the JWT, you can disable verification for better performance.

Example:

import jwt

# Disable verification
token = jwt.decode({'data': 'my_data'}, 'secret', algorithms=['HS256'], verify=False)

# Enable verification (default)
token = jwt.decode({'data': 'my_data'}, 'secret', algorithms=['HS256'])

3. Cache JWTs

If a JWT will be used multiple times, it can be cached to avoid re-decoding.
This can significantly improve performance.

Example:

import jwt, time

# Create a JWT
token = jwt.encode({'data': 'my_data'}, 'secret', algorithm='HS256')

# Cache the JWT
cache = {}
cache[token] = time.time()

# Retrieve the cached JWT
if token in cache:
    # Check if the JWT is still valid
    if time.time() - cache[token] < 600:  # 10 minutes
        return jwt.decode(token, 'secret', algorithms=['HS256'])

# Decoded the JWT (if not cached)
return jwt.decode(token, 'secret', algorithms=['HS256'])

4. Use a Faster Library

PyJWT is a popular JWT library, but it may not be the fastest.
There are other faster libraries available, such as jose.

5. Use a C-based Library

C-based libraries are generally faster than Python-based libraries.
There are JWT libraries written in C, such as pyca/cryptography.

Real World Applications

Authentication: JWTs can be used to authenticate users in web applications. Using a faster algorithm can improve the response time of login requests.
Authorization: JWTs can be used to authorize users to access certain resources. Caching JWTs can reduce the number of database calls required to verify permissions.
Data Exchange: JWTs can be used to securely exchange data between different systems. Using a faster library can speed up the data transfer process.

Security best practices

1. Use a Strong Algorithm

In plain English: Choose a tough lock for your door, such as "AES" or "RSA," so that it's hard for others to pick.
Improved code snippet:

from pyjwt import JWT, algorithms

# Create a JSON Web Token with a strong algorithm
token = JWT()
token.encode(payload, "your-strong-secret-key", algorithm=algorithms.RSA256)

# Decode the token, verifying it with the same algorithm
payload = JWT().decode(token, "your-strong-secret-key", algorithms=["RSA256"])

2. Use a Long Enough Secret Key

In plain English: Make your key as long as a strong password, at least 256 bits.
Improved code snippet:

# Create a long, random secret key
secret_key = os.urandom(32)  # 32 bytes = 256 bits

# Encode and decode a token using the long secret key
token = JWT().encode(payload, secret_key, algorithm=algorithms.HS256)
payload = JWT().decode(token, secret_key, algorithms=["HS256"])

3. Store Your Secret Key Safely

In plain English: Keep your key a secret! Don't write it on paper or mail it to anyone.
Improved code snippet:

import os

# Store your secret key securely in an environment variable
os.environ["JWT_SECRET_KEY"] = "your-strong-secret-key"

# Access the secret key from the environment variable
secret_key = os.environ["JWT_SECRET_KEY"]

# Encode and decode a token using the secret key
token = JWT().encode(payload, secret_key, algorithm=algorithms.HS256)
payload = JWT().decode(token, secret_key, algorithms=["HS256"])

4. Verify Signature

In plain English: When receiving a token, check that its lock (signature) was made with the right key and not tampered with.
Improved code snippet:

# Verify the signature of a token using a public key
public_key = os.path.join(os.path.dirname(__file__), "public.pem")
with open(public_key) as f:
    key = RSA.import_key(f.read())

# Decode the token, verifying its signature
payload = JWT().decode(token, key, algorithms=["RS256"])

5. Validate Audience

In plain English: Make sure the token is meant for your application and not for someone else.
Improved code snippet:

# Specify the audience when encoding a token
token = JWT().encode(
    payload, secret_key, audience="your-application-url", algorithm=algorithms.HS256
)

# Validate the audience when decoding a token
payload = JWT().decode(
    token,
    secret_key,
    algorithms=["HS256"],
    audience="your-application-url",
)

6. Validate Issuer

In plain English: Check that the token came from a trusted sender.
Improved code snippet:

# Specify the issuer when generating a token
token = JWT()
token.encode(
    payload, secret_key, issuer="your-application-url", algorithm=algorithms.RS256
)

# Validate the issuer when decoding a token
payload = JWT().decode(
    token,
    secret_key,
    algorithms=["RS256"],
    issuer="your-application-url",
)

7. Validate Expiration

In plain English: Ensure the token hasn't expired yet.
Improved code snippet:

# Specify the expiration time when generating a token
token = JWT()
token.encode(
    payload,
    secret_key,
    exp=datetime.utcnow() + timedelta(hours=1),
    algorithm=algorithms.HS256,
)

# Validate the expiration time when decoding a token
payload = JWT().decode(token, secret_key, algorithms=["HS256"])

8. Validate Not Before Time

In plain English: Make sure the token can be used right now and not in the future.
Improved code snippet:

# Specify the not before time when generating a token
token = JWT()
token.encode(
    payload,
    secret_key,
    nbf=datetime.utcnow(),
    algorithm=algorithms.HS256,
)

# Validate the not before time when decoding a token
payload = JWT().decode(token, secret_key, algorithms=["HS256"])

9. Validate Subject

In plain English: Check that the token represents the user you expect.
Improved code snippet:

# Specify the subject when generating a token
token = JWT()
token.encode(
    payload,
    secret_key,
    subject="your-user-id",
    algorithm=algorithms.HS256,
)

# Validate the subject when decoding a token
payload = JWT().decode(token, secret_key, algorithms=["HS256"])

10. Validate JWT ID

In plain English: Make sure each token is unique, like a fingerprint.
Improved code snippet:

# Specify the JWT ID when generating a token
token = JWT()
token.encode(
    payload,
    secret_key,
    jwt_id="a-unique-identifier",
    algorithm=algorithms.HS256,
)

# Validate the JWT ID when decoding a token
payload = JWT().decode(token, secret_key, algorithms=["HS256"])

Real-World Applications:

These best practices are essential for securing any application that uses JWTs to authenticate users or handle sensitive data. For example:

Authentication: Verify that a user is who they claim to be before granting access to restricted resources.
Authorization: Control what actions a user can perform based on their role or permissions.
Data Integrity: Protect data from being tampered with or corrupted by ensuring that JWTs are signed and validated properly.

Usage with FastAPI

FastAPI is a modern, high-performance web framework for building APIs in Python. It provides a powerful set of features for creating and securing APIs.

PyJWT is a Python library for creating and decoding JSON Web Tokens (JWTs). JWTs are a secure way to represent claims (such as user identity) between two parties, and are often used to authenticate users and authorize access to resources.

FastAPI and PyJWT can be used together to create secure APIs that use JWTs for authentication and authorization.

Installing PyJWT

To install PyJWT, run the following command:

pip install pyjwt

Creating a JWT

A JWT is created using the jwt.encode() function. The function takes three arguments:

The claims to be encoded
The secret key used to sign the JWT
The algorithm to use for signing (e.g., HS256)

import jwt

claims = {
    "username": "alice",
    "email": "alice@example.com",
}

secret_key = "my-secret-key"
algorithm = "HS256"

encoded_jwt = jwt.encode(claims, secret_key, algorithm)

The encoded_jwt variable now contains a JWT that can be used to authenticate the user.

Decoding a JWT

A JWT can be decoded using the jwt.decode() function. The function takes three arguments:

The JWT to be decoded
The secret key used to verify the JWT
The algorithm used to sign the JWT

import jwt

secret_key = "my-secret-key"
algorithm = "HS256"

decoded_jwt = jwt.decode(encoded_jwt, secret_key, algorithms=[algorithm])

The decoded_jwt variable now contains the claims that were encoded in the JWT.

Using PyJWT with FastAPI

PyJWT can be used with FastAPI to create secure APIs that use JWTs for authentication and authorization.

Authentication

PyJWT can be used to authenticate users by verifying the JWT they provide in the request. This can be done using a middleware function.

from fastapi import FastAPI, HTTPException
from fastapi.middleware.authentication import BasicAuthenticationMiddleware

app = FastAPI()

app.add_middleware(
    BasicAuthenticationMiddleware,
    backend=AuthBackend(),
)

class AuthBackend:
    def __init__(self):
        self.secret_key = "my-secret-key"
        self.algorithm = "HS256"

    async def authenticate(self, username: str, password: str):
        try:
            decoded_jwt = jwt.decode(username, self.secret_key, algorithms=[self.algorithm])
        except jwt.exceptions.PyJWTError:
            return False

        return decoded_jwt["username"] == username

Authorization

PyJWT can also be used to authorize users to access certain resources. This can be done by adding a @jwt_required() decorator to the endpoint.

@app.post("/protected")
@jwt_required()
async def protected(username: str):
    return {"message": "Hello, {}".format(username)}

The @jwt_required() decorator will verify the JWT in the request and ensure that the user has the necessary permissions to access the endpoint.

Real-World Applications

PyJWT can be used in a variety of real-world applications, including:

Authentication: PyJWT can be used to authenticate users in a variety of applications, including web applications, mobile applications, and APIs.
Authorization: PyJWT can be used to authorize users to access certain resources, such as files, databases, or APIs.
Data exchange: PyJWT can be used to securely exchange data between two parties, such as a client and a server.

Conclusion

PyJWT is a powerful library for creating and decoding JWTs. It can be used with FastAPI to create secure APIs that use JWTs for authentication and authorization.

Token deserialization

Token Deserialization

What is Token Deserialization?

It's like opening a letter: you take the envelope (the token) and turn it into the message inside (the data in the token).

How does it work?

Get the Token: You get the token from somewhere, like an email or a website.
Decode the Token: You use a special "decoder key" (a secret word) to decode the token into its parts:
- Header: Information about the token, like who created it and when.
- Payload: The actual data in the token, like your username.
- Signature: A special code that checks if the token hasn't been tampered with.
Verify the Token: You check if the signature matches the header and payload to make sure the token is valid.

Code Snippet:

import jwt

# Example token
token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ1c2VybmFtZSI6InVzZXJuYW1lIiwiaWF0IjoxNjU1NzY1MzIxfQ.cpq_0QAAp1iJAA_B76zR-cAqFJ44jy3Xdo6YPW0yc_A"

# Decode the token
decoded_token = jwt.decode(token, "your_secret_key", algorithms=["HS256"])

# Print the decoded token
print(decoded_token)

Real-World Applications:

Authentication: Ensure users are who they say they are when logging in to websites or apps.
Authorization: Control who can access certain data or features based on their身份.
Data exchange: Securely share data between different systems or applications.

Payload parameters

Payload Parameters

When creating a JWT, you can specify a payload, which is a dictionary of claims that you want to include in the token. The following table describes the parameters you can use to specify the payload:

Parameter

Description

Example

iat

The time the token was issued.

1577836800

exp

The time the token expires.

1577836800

nbf

The time before which the token is not valid.

1577836800

jti

A unique identifier for the token.

"a987bcde-4321-0987-cdef-1234567890ab"

iss

The issuer of the token.

"example.com"

sub

The subject of the token.

"alice@example.com"

aud

The intended audience of the token.

["example.com", "example.org"]

Example:

The following code shows how to create a JWT with a payload:

import jwt

payload = {"iat": 1577836800, "exp": 1577836800, "sub": "alice@example.com"}
token = jwt.encode(payload, "secret", algorithm="HS256")

This will create a JWT with a payload that contains the following claims:

iat: 1577836800 (the time the token was issued)
exp: 1577836800 (the time the token expires)
sub: "alice@example.com" (the subject of the token)

Applications:

JWTs are used in a variety of applications, including:

Authentication: JWTs can be used to authenticate users to web services.
Authorization: JWTs can be used to authorize users to access resources.
Data exchange: JWTs can be used to exchange data between different parties.

Stateless authentication

Stateless Authentication

Imagine your favorite online game where you create a character and log in to play.

What is Stateless Authentication?

It's like a digital key that you use to prove who you are when you log in. It's "stateless" because it doesn't store any information about you on the server.

How it Works:

Create a JWT (key): The server creates a unique key, like a puzzle piece, that contains your username and other essential information.
Sign the JWT: The server signs the key with its secret code, like a unique fingerprint. This ensures that the key hasn't been tampered with.
Send the JWT to You: The server sends the signed key to you, like a digital pass.
Store the JWT: You store the key securely, like in a cookie or local storage.
Request Access: When you try to access the game, you send the key back to the server.
Server Verifies: The server uses its secret code to verify the key and makes sure it's valid and not fake.
Grant Access: If the key is valid, the server grants you access to play.

Code Example:

import jwt

# Create a JWT token
token = jwt.encode({'username': 'john'}, 'secret_key')

# Verify the JWT token
decoded_token = jwt.decode(token, 'secret_key')
username = decoded_token['username']

# Grant access
if username == 'john':
    print("Welcome, John!")

Real-World Applications:

Online games: Verifying players' identities without storing their passwords.
E-commerce websites: Allowing customers to log in without creating accounts.
API authentication: Granting access to APIs based on JWTs.
Mobile apps: Providing seamless login experiences across devices.

Token refreshing

Token Refreshing in JWT

Introduction:

In JSON Web Tokens (JWT), a token's lifespan is limited. For security reasons, it's recommended to use tokens with short expiry times. However, long-lived sessions require frequent token replacements, which can be inefficient. Token refreshing addresses this issue by allowing clients to obtain new tokens without requiring user re-authentication.

Concepts:

1. Refresh Token:

A token issued to clients that allows them to exchange it for a new JWT (access token).
Typically has a longer expiry time than access tokens.
Stored securely on the client side.

2. Access Token:

The actual token used for authorization and authentication.
Has a shorter expiry time and is used for specific actions.
Issued upon successful validation of the refresh token.

3. Refresh Token Rotation:

Periodically generating a new refresh token to enhance security.
Prevents attackers from exploiting compromised refresh tokens for extended periods.

How it Works:

Client Requests Access Token: The client sends a request to the authorization server with the refresh token.
Server Validates Refresh Token: The server verifies the validity of the refresh token, including its signature, expiry time, and issuer.
New Access Token Issued: If the token is valid, the server generates a new access token and sends it to the client.
Refresh Token Rotation (Optional): The server may also issue a new refresh token with an updated expiry time for increased security.

Implementation:

from jose import jwt
from datetime import datetime, timedelta

# Define the secret key used to sign the tokens
SECRET_KEY = "my-secret-key"

# Define the issuer
ISSUER = "my-issuer"

# Define the audience
AUDIENCE = "my-audience"

# Define the expiry time for access tokens (e.g., 5 minutes)
ACCESS_TOKEN_EXPIRES = timedelta(minutes=5)

# Define the expiry time for refresh tokens (e.g., 1 hour)
REFRESH_TOKEN_EXPIRES = timedelta(hours=1)

# Function to generate a new access token
def create_access_token(subject):
    now = datetime.utcnow()

    payload = {
        "sub": subject,
        "iat": now,
        "exp": now + ACCESS_TOKEN_EXPIRES,
        "iss": ISSUER,
        "aud": AUDIENCE
    }

    encoded_token = jwt.encode(payload, SECRET_KEY, algorithm="HS256")

    return encoded_token

# Function to generate a new refresh token
def create_refresh_token(subject):
    now = datetime.utcnow()

    payload = {
        "sub": subject,
        "iat": now,
        "exp": now + REFRESH_TOKEN_EXPIRES,
        "iss": ISSUER,
        "aud": AUDIENCE
    }

    encoded_token = jwt.encode(payload, SECRET_KEY, algorithm="HS256")

    return encoded_token

# Function to refresh an access token using a refresh token
def refresh_access_token(refresh_token):
    decoded_refresh_token = jwt.decode(refresh_token, SECRET_KEY, algorithms=["HS256"])

    new_access_token = create_access_token(decoded_refresh_token["sub"])

    return new_access_token

Real-World Applications:

Long-lived Sessions: For applications where sessions need to persist for extended periods (e.g., single sign-on).
Mobile Applications: Easily renew tokens without requiring user interaction, enhancing UX.
APIs: Enable clients to securely update their tokens without compromising API security.

Additional Considerations:

Store refresh tokens securely using encrypted databases or HTTP-only cookies.
Implement refresh token rotation to mitigate the risk of compromised tokens.
Limit the number of token refreshes per client to prevent abuse.

JSON Web Key (JWK)

Introduction

A JWK (JSON Web Key) is a digital key that is represented in JSON. It is used in JSON Web Tokens (JWTs) to digitally sign or encrypt the token.

Components of a JWK

A JWK consists of the following components:

Key ID (kid): A unique identifier for the key.
Key Type (kty): The type of key (e.g., RSA, EC).
Public Key: The actual public key used for signing or encrypting.

Types of JWKs

There are two main types of JWKs:

Public JWK: Used to verify signatures or decrypt data.
Private JWK: Used to create signatures or encrypt data.

How JWKs are Used in JWTs

JWKs are used in JWTs to digitally sign or encrypt the token. The following steps are involved:

1. Generate a JWK.
2. Use the JWK to create a JWT.
3. Send the JWT to the recipient.
4. The recipient uses the JWK to verify the signature or decrypt the JWT.

Real-World Applications

JWKs are used in various applications, including:

API Authentication: For authenticating users to access APIs.
Secure Data Exchange: For exchanging sensitive data securely over the internet.
Blockchain Applications: For verifying the authenticity of transactions on a blockchain.

Code Example

Here's a Python example using the pyjwt library to generate a JWT with a JWK:

import jwt

# Generate a JWK
private_key = "-----BEGIN PRIVATE KEY-----\n..."
public_key = "-----BEGIN PUBLIC KEY-----\n..."
jwk = {"kid": "my-key", "kty": "RSA", "n": public_key}

# Create a JWT
jwt_token = jwt.encode({"data": "Hello world!"}, private_key, "RS256", algorithm="RS256", headers={"kid": "my-key"})

# Decode the JWT with the public JWK
decoded_jwt = jwt.decode(jwt_token, public_key, algorithms=["RS256"])

JSON Web Key Set (JWKS)

JSON Web Key Set (JWKS)

What is it?

Imagine you have a secret box and you want to share its contents with your friends. Instead of giving them the key, you create a bunch of smaller keys and give them out. Each key can only unlock a certain part of the box.

Use Case: In digital world, JWKS is used to verify the authenticity of JSON Web Tokens (JWTs). A JWT is like a digital passport that contains information about who you are and what you're allowed to do. JWKS helps make sure that the passport is real and not a fake.

How it Works:

Public Key: Each key in the JWKS is like a lock. It's publicly available, so anyone can use it to encrypt a message.
Private Key: The secret box has a master key that can open the entire box. This is the private key, and it's kept secret.
Signature Verification: When someone gives you a JWT, you use a public key from the JWKS to verify that it's real. If the public key can unlock the encrypted parts of the JWT, then you know the JWT is authentic.

Example:

Imagine a school principal wants to create a JWT for a student.

Public Key: The principal creates a public key pair. The public key is stored in the JWKS and made available to everyone.
Private Key: The principal keeps the private key secret.
JWT Creation: The principal creates a JWT, encrypts it using the private key, and signs it using the public key.
JWT Verification: When the student presents the JWT to the school, the school uses the public key from the JWKS to verify the signature. If the signature is valid, then the school knows the JWT is real and can trust the information inside.

Real-World Applications:

Authentication: JWTs are commonly used for authentication, ensuring that users are who they claim to be.
Authorization: JWTs can contain information about a user's permissions and access levels.
Data Exchange: JWTs can be used to securely transmit data between systems or applications.

Security considerations

Security Considerations

1. Token Expiration

Explanation: A JWT has an expiration date, after which it becomes invalid. This is important to prevent the token from being used after it should have expired.
Simplified: Imagine a token as a passcode that lets you into a secret room. The expiration date is like the time the passcode expires, and after that time, it no longer works. Code Example:

import jwt
from datetime import datetime

# Create a JWT with an expiration date of 1 hour from now
token = jwt.encode({
    "data": "My secret data",
}, "secret", algorithm="HS256")

2. Token Signing

Explanation: A JWT is signed using a secret key, and the signature ensures that the token has not been tampered with.
Simplified: Imagine a box of chocolates. The signature is like a seal that shows that the box has not been opened and the chocolates are still safe to eat. Code Example:

import jwt
from datetime import datetime

# Create a JWT signed with a secret key
token = jwt.encode({
    "data": "My secret data",
}, "secret", algorithm="HS256")

# Verify the signature of a JWT
try:
    data = jwt.decode(token, "secret", algorithms=["HS256"])
    print(data["data"])
except jwt.InvalidSignatureError:
    print("The JWT signature is invalid")

3. Token Validation

Explanation: Before using a JWT, it should be validated to ensure that it is valid and has not been compromised.
Simplified: Imagine a friend gives you a message saying they will meet you at a certain place at a certain time. You should confirm with your friend that they really sent the message and that they haven't changed their plans. Code Example:

import jwt
from datetime import datetime

# Validate a JWT
try:
    data = jwt.decode(token, "secret", algorithms=["HS256"])
    print(data["data"])
except jwt.exceptions.InvalidTokenError:
    print("The JWT is invalid")

4. Best Practices

Use a secure signing algorithm.
Set a reasonable token expiration time.
Store the secret key securely.
Use a trusted library for JWT handling.

Real-World Applications:

Authentication: JWTs can be used to authenticate users by providing them with a token that can be verified by a server.
Authorization: JWTs can be used to authorize users to access specific resources by including information about the user's permissions in the token.
Data Exchange: JWTs can be used to securely share data between different services or applications.

Common pitfalls

Common Pitfalls

1. Using the wrong encoding algorithm:

JWTs can be encoded using different algorithms, such as HS256, RS256, and ES256.
If you specify the wrong algorithm when creating or verifying a JWT, it will fail.

Simplified Explanation:

Imagine JWTs as secret messages. You can choose different "codes" to encrypt and decrypt them. If you use the wrong code, you won't be able to read the message.

Code Example:

import jwt

# Create a JWT with the wrong algorithm
token = jwt.encode({'payload': 'secret'}, 'wrong_algorithm', algorithm='HS256')

# Verify the JWT with the correct algorithm
try:
    jwt.decode(token, 'correct_algorithm')
except jwt.DecodeError:
    print('Invalid token')

2. Using a secret key that is too short:

JWTs are signed with a secret key, which is used to verify their authenticity.
If the secret key is too short, it can be easily guessed or cracked.

Simplified Explanation:

Think of the secret key as the password to your secret message. If your password is too short, it's easy to guess.

Code Example:

# Create a JWT with a short secret key
token = jwt.encode({'payload': 'secret'}, 'my_short_key')

# Verify the JWT with the same secret key
jwt.decode(token, 'my_short_key')  # This will succeed

3. Not setting the expiration time:

JWTs can have an expiration time, after which they will no longer be valid.
If you do not set an expiration time, the JWT will be valid indefinitely.

Simplified Explanation:

JWTs are like tickets. If you don't set an expiration time, the ticket will never expire. Anyone could use it to access your secret message.

Code Example:

# Create a JWT without an expiration time
token = jwt.encode({'payload': 'secret'})

# Verify the JWT indefinitely
jwt.decode(token)  # This will always succeed

4. Not using a secure connection when transmitting JWTs:

JWTs should be transmitted over a secure connection, such as HTTPS.
If you transmit JWTs over an insecure connection, they could be intercepted and stolen.

Simplified Explanation:

Imagine sending a secret message over an unencrypted email. Anyone could read the message while it's being sent.

Code Example:

# Send a JWT over an insecure connection
import requests

requests.get('http://example.com/api/v1/secret', headers={'Authorization': 'Bearer {}'.format(token)})

5. Storing JWTs in a browser's local storage:

Browsers' local storage is not secure.
If a user's browser is compromised, an attacker could access the JWTs stored in local storage.

Simplified Explanation:

Think of your browser's local storage as a small box where you keep secrets. If someone breaks into your box, they can steal your secrets.

Code Example:

// Store a JWT in a browser's local storage
localStorage.setItem('jwt', token);

Potential Applications in the Real World:

Authentication: JWTs can be used to authenticate users in web applications and APIs.
Authorization: JWTs can be used to authorize users to access specific resources or perform certain actions.
Data exchange: JWTs can be used to securely exchange data between different systems or services.

Token serialization

Token Serialization

What is token serialization?

Token serialization is the process of converting a token (a piece of data that represents something else) into a string of characters that can be stored or transmitted.

Why serialize tokens?

Tokens are often serialized so that they can be:

Stored: Tokens can be stored in a database or file for later use.
Transmitted: Tokens can be sent over a network to other parties.

How to serialize tokens

Tokens can be serialized using a variety of algorithms, including:

JSON Web Token (JWT): JWT is a popular token serialization format that is based on JSON. JWT tokens are typically used to represent user authentication and authorization.
Secure Hash Algorithm (SHA): SHA is a family of cryptographic hash functions that can be used to create a unique fingerprint of data. SHA tokens are often used to represent user passwords.
Base64: Base64 is an encoding scheme that can be used to convert binary data into a string of characters. Base64 tokens are often used to represent images or other binary data.

Code example

The following Python code shows how to serialize a token using the JWT algorithm:

import jwt

token = jwt.encode({'username': 'user1', 'password': 'pass1'}, 'secret')

Real-world applications

Token serialization is used in a variety of real-world applications, including:

User authentication and authorization: JWT tokens are often used to authenticate users and authorize them to access resources.
Password storage: SHA tokens are often used to store user passwords in a secure way.
Data storage: Base64 tokens are often used to store images or other binary data in a database or file.

Token signing

Token Signing

What is token signing?

Imagine you're sending a secret message to your friend. You don't want anyone else to read it, so you use a special code to encrypt the message. This is similar to what token signing does.

How does it work?

Create a secret key: This is a special code that only you and the person you're sending the message to know.
Encode the message: You use the secret key to encrypt the message.
Add a signature: You add a special code to the end of the message called a signature. This code is created using the secret key and the encoded message.

Why is it important?

Token signing helps to ensure that:

The message wasn't changed: The receiver can check the signature to make sure it hasn't been tampered with.
The message is authentic: Only the person who knows the secret key can create a valid signature.

Code Example

import jwt

# Create a secret key
secret_key = "my_super_secret_key"

# Create a message to encode
message = {"name": "John", "age": 30}

# Encode the message using the HS256 algorithm
encoded_message = jwt.encode(message, secret_key, algorithm="HS256")

# Add a signature to the message
signature = jwt.encode(encoded_message, secret_key, algorithm="HS256")

# The final signed token is a combination of the encoded message and the signature
token = encoded_message + "." + signature

Real-World Applications

Authentication: Verifying a user's identity by checking the signature of their token.
Authorization: Granting or denying access to resources based on the contents of the token.
Secure communication: Exchanging encrypted messages between trusted parties.

Custom validation

Custom Validation

In PyJWT, you can validate JWTs using custom validation rules besides the default ones. This allows you to add your own logic to ensure that the JWT meets specific criteria.

Custom Validations

To create a custom validation, you implement a class that inherits from pyjwt.PyJWTValidation. The class must override the validate_payload method. Here's a simplified template:

import jwt

class MyCustomValidation(jwt.PyJWTValidation):
    def validate_payload(self, payload, **kwargs):
        # Implement your custom validation logic here
        return True  # Validation passed

Validation Logic

In the validate_payload method, you define the logic to verify the payload. For example, you could check for the presence of a specific field:

def validate_payload(self, payload, **kwargs):
    if "custom_field" not in payload:
        raise jwt.JWTError("Missing 'custom_field' field")
    return True

Using Custom Validations

To apply your custom validation, pass it as the options parameter to the jwt.decode() method:

from my_custom_validation import MyCustomValidation

my_options = {
    "verify_signature": False,
    "validate_aud": False,
    "validate_iss": False,
    "validate_exp": False,
    "validate_nbf": False,
    "validate_iat": False,
    "validation_class": MyCustomValidation
}

token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"

payload = jwt.decode(token, verify=False, options=my_options)
print(payload)

This will decode the JWT without verifying the default parameters and instead apply your custom validation defined in MyCustomValidation.

Potential Applications

Custom validations can be used in various scenarios, such as:

Enforcing specific claims: Ensuring that the JWT contains specific claims or values.
Verifying role-based access: Restricting access to resources based on the roles or permissions specified in the payload.
Checking authorization: Verifying that the JWT is authorized to perform a certain action.
Detecting JWT tampering: Identifying if the JWT has been modified or tampered with before validation.

Documentation and resources

Documentation and Resources

1. Installation

Install pyJWT using pip: pip install pyjwt

2. Encoding and Decoding

Encoding: Create a JWT token by passing a payload (data), a secret key, and an algorithm.

import jwt
payload = {'username': 'alice'}
secret_key = 'my_super_secret_key'
token = jwt.encode(payload, secret_key, algorithm='HS256')

Decoding: Extract the payload from a JWT token by providing the token, secret key, and algorithm.

token = 'your_encoded_token'
secret_key = 'my_super_secret_key'
payload = jwt.decode(token, secret_key, algorithms=['HS256'])

3. Header and Claims

Header: Contains information about the token's algorithm and type.
Claims: Represent the actual data in the token, such as the payload and other additional information.

4. Algorithms

pyJWT supports various algorithms, including:
- HMAC-based: HS256, HS384, HS512
- RSA-based: RS256, RS384, RS512
- Elliptic Curve-based: ES256, ES384, ES512

5. Real-World Applications

User authentication: Generate JWT tokens for users to access authenticated areas of an application.
Data integrity: Ensure data hasn't been tampered with by validating JWT tokens containing data signatures.
Cross-system communication: Exchange data securely between different systems using JWT tokens.

Complete Code Implementation

import jwt

# Encode a JWT token
payload = {'username': 'alice'}
secret_key = 'my_super_secret_key'
token = jwt.encode(payload, secret_key, algorithm='HS256')

# Decode a JWT token
token = 'your_encoded_token'
secret_key = 'my_super_secret_key'
payload = jwt.decode(token, secret_key, algorithms=['HS256'])

# Use a JWT token for user authentication
def authenticate_user(token):
  try:
    payload = jwt.decode(token, 'secret_key')
    return payload['username']
  except jwt.ExpiredSignatureError:
    return None

JWT format

Header

The header contains the following information:

typ: The type of token. This is usually set to "JWT".
alg: The algorithm used to sign the token.

Payload

The payload contains the claims. Claims are statements about the token, such as:

iss: The issuer of the token.
sub: The subject of the token.
aud: The audience of the token.
exp: The expiration time of the token.

Signature

The signature is created by hashing the header and payload using the algorithm specified in the header. The signature is then encrypted using the private key of the issuer.

Example

The following is an example of a JWT:

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJqb2UiLCJzdWIiOiJzb21lYm9keSIsImF1ZCI6ImV2ZXJ5b25lIn0.H0uV_tEKm_4x84u_r5k-Ny8oqv0j0j4w7q7Fy4txa18

Applications

JWTs are used in a variety of applications, including:

Authentication: JWTs can be used to authenticate users to a web service.
Authorization: JWTs can be used to authorize users to access certain resources.
Data exchange: JWTs can be used to exchange data between different parties.

Potential applications in Real world:

Single Sign-On (SSO): JWT can be used to enable Single Sign-On (SSO) across multiple applications. This allows users to log in once and access multiple applications without having to re-enter their credentials for each application.

Here's an example of how JWT can be used for SSO:

User logs into Application A using their credentials.
Application A generates a JWT and sends it to the user's browser.
User visits Application B.
Application B reads the JWT from the user's browser and verifies it.
If the JWT is valid, Application B grants the user access to the application.

API authentication: JWT can be used to authenticate users to an API. This allows developers to easily secure their APIs and prevent unauthorized access.

Here's an example of how JWT can be used for API authentication:

User sends a request to an API.
The request includes a JWT in the authorization header.
The API server verifies the JWT.
If the JWT is valid, the API server grants the user access to the requested resource.

Data exchange: JWT can be used to exchange data between different parties. This allows parties to securely share data without having to worry about data breaches or unauthorized access.

Here's an example of how JWT can be used for data exchange:

Party A generates a JWT containing some data.
Party A sends the JWT to Party B.
Party B verifies the JWT.
If the JWT is valid, Party B can access the data contained in the JWT.

Algorithm selection (HS256, HS384, HS512, RS256, RS384, RS512, ES256, ES384, ES512)

Algorithm Selection for JWT

When creating or validating a JWT (JSON Web Token), you need to select an algorithm to use. An algorithm is a mathematical function that ensures the security and integrity of the token. There are several algorithms available:

HMAC-based Algorithms:

HS256: Uses a 256-bit secret key for hashing.
HS384: Uses a 384-bit secret key for hashing.
HS512: Uses a 512-bit secret key for hashing.

RSA-based Algorithms:

RS256: Uses a 256-bit RSA private key for signing.
RS384: Uses a 384-bit RSA private key for signing.
RS512: Uses a 512-bit RSA private key for signing.

ECDSA-based Algorithms:

ES256: Uses a 256-bit elliptic curve private key for signing.
ES384: Uses a 384-bit elliptic curve private key for signing.
ES512: Uses a 512-bit elliptic curve private key for signing.

Choosing an Algorithm:

HS algorithms are simple and efficient, but less secure than RSA or ECDSA. They should only be used in situations where security is not paramount.
RSA algorithms are more secure than HS algorithms, but they are slower and can be more computationally expensive.
ECDSA algorithms are the most secure and provide a good balance of performance and security.

Real-World Implementations:

Python (using PyJWT):

# Import the library
import jwt

# Create a JWT with the HS256 algorithm
token = jwt.encode({'some': 'payload'}, 'secret', algorithm='HS256')

# Decode the JWT
decoded_token = jwt.decode(token, 'secret', algorithms=['HS256'])

Go (using jose):

import (
    "github.com/square/go-jose/v3"
)

// Create a JWT with the RS256 algorithm
token, err := jose.NewSigner(
    jose.SigningKey{Algorithm: jose.RS256, Key: privateKey},
    (&jose.SignerOptions{}).WithType("JWT"),
).Sign(payload)

// Decode the JWT
verifier, err := jose.NewVerifier(
    jose.SigningKey{Algorithm: jose.RS256, Key: publicKey},
)

if verifier == nil {
    // Error handling
}

payload, err := verifier.Verify(token)

Potential Applications:

Authentication: JWTs can be used to authenticate users to online services without the need for passwords.
Authorization: JWTs can be used to authorize users to access specific resources.
Data Exchange: JWTs can be used to securely exchange data between different systems or applications.

Token introspection

Token Introspection

Imagine you have a secret box that you want to give to your friend. To make sure only your friend can open it, you give them a key. If they lose the key, you don't want anyone else to be able to open the box.

Token introspection is like checking the key for the secret box. It's a way to make sure that the token you received is valid and was meant for you.

How Token Introspection Works

When you create a token, you include information about who it belongs to and when it expires. Token introspection checks this information to make sure it's still valid.

The token is sent to an introspection endpoint. This is a special website or server that can check tokens.
The introspection endpoint checks the token's signature. This makes sure that the token has not been tampered with.
The introspection endpoint checks the token's claims. These are the pieces of information inside the token, like who it belongs to and when it expires.

If all the checks pass, the introspection endpoint sends back a response saying that the token is valid. If any of the checks fail, the endpoint sends back an error message.

Code Example

import jwt

# Create a token
token = jwt.encode({'name': 'John Doe'}, 'secret', algorithm='HS256')

# Introspect the token
introspect_endpoint = 'https://example.com/introspection'
response = requests.post(introspect_endpoint, data={'token': token})

# Check the response
if response.status_code == 200:
    print('The token is valid.')
else:
    print('The token is not valid.')

Real-World Applications

Token introspection is used in many applications, including:

Authentication: Checking if a user is logged in.
Authorization: Checking if a user has permission to access a resource.
Fraud detection: Making sure that tokens are not being used fraudulently.

Custom algorithms

Custom Algorithms

Sometimes, you might need to use a custom algorithm for your JWTs. This is great if you have a specific security requirement that is not met by the standard algorithms.

Creating a Custom Algorithm

To create a custom algorithm, you'll need to implement the JWTAlgorithm class. This class has three methods:

encode() - This method takes the header, payload, and secret key and returns the encoded JWT.
decode() - This method takes the encoded JWT and secret key and returns the header, payload, and signature.
verify() - This method takes the encoded JWT, secret key, and public key (if applicable) and returns True if the JWT is valid, or False if it is not.

Example

The following is an example of a custom algorithm that uses a simple XOR cipher:

import base64

class XORAlgorithm(JWTAlgorithm):
    def encode(self, header, payload, secret_key):
        encoded_header = base64.urlsafe_b64encode(header.encode('utf-8')).decode('utf-8')
        encoded_payload = base64.urlsafe_b64encode(payload.encode('utf-8')).decode('utf-8')
        signature = ''.join(chr(ord(ch) ^ ord(s)) for ch,s in zip(encoded_payload, secret_key))
        return f'{encoded_header}.{encoded_payload}.{signature}'

    def decode(self, encoded_jwt, secret_key):
        header, payload, signature = encoded_jwt.split('.')
        decoded_payload = ''.join(chr(ord(ch) ^ ord(s)) for ch,s in zip(payload, secret_key))
        return base64.urlsafe_b64decode(header).decode('utf-8'), base64.urlsafe_b64decode(decoded_payload).decode('utf-8'), signature

    def verify(self, encoded_jwt, secret_key, public_key=None):
        return True  # Implement your own verification logic here

# Usage
payload = {'foo': 'bar'}
jwt = JWT(algorithm=XORAlgorithm())
encoded_jwt = jwt.encode(payload, 'secret')
print(encoded_jwt)

Real-World Applications

Custom algorithms can be used in a variety of real-world applications, including:

Encryption with non-standard algorithms - If you need to use a specific encryption algorithm that is not supported by the standard JWT algorithms, you can create a custom algorithm to implement it.
Adding additional security measures - You can use a custom algorithm to add additional security measures to your JWTs, such as salting or hashing the payload.
Implementing custom authorization schemes - You can use a custom algorithm to implement a custom authorization scheme for your JWTs.

Token verification

Token Verification

What is Token Verification?

When you receive a token, you want to make sure it's valid and not fake or altered. Token verification is the process of checking if the token is authentic and hasn't been tampered with.

How to Verify a Token?

To verify a token, you need a secret key. This key is like a password that was used to create the token.

Get the secret key: This key should be kept securely on your server.
Decode the token: Use the secret key and a library (like PyJWT) to decode the token.
Check the expiration time: Make sure the token has not expired.
Check the issuer: Verify if the token was issued by a trusted source.
Check the audience: Ensure the token was intended for your website or app.

Example in Python:

import jwt

secret = "my_secret_key"

def verify_token(token):
    data = jwt.decode(token, secret, algorithms=["HS256"])
    # Check expiration time, issuer, audience, etc.
    return data

Real-World Applications:

Authentication: Verify user's identity when they log in.
Authorization: Check if a user has permission to access a specific resource.
Data Integrity: Ensure that data transmitted over the network has not been altered.

Simplify and Explain:

Let's say you have a token like "abc XYZ 123". The secret key is like a password that unlocks the token and allows you to verify it.

You would use a library like PyJWT to "decode" the token, which means to unlock it using the secret key. If the token is valid, you get access to the information stored inside, such as the user's name or role.

Code Snippet Improvement:

import jwt

secret = "my_secret_key"

def verify_token(token):
    try:
        data = jwt.decode(token, secret, algorithms=["HS256"])
    except jwt.ExpiredSignatureError:
        return "Token expired"
    except jwt.InvalidTokenError:
        return "Invalid token"
    # Check expiration time, issuer, audience, etc.
    return data

This improved code snippet handles common errors and provides more descriptive return values to help debugging.

Usage with Flask

Usage with Flask (Simplified)

Introduction

Flask is a popular Python web framework. pyjwt can be integrated with Flask to secure your APIs by creating and verifying JSON Web Tokens (JWTs).

Creating JWTs

To create a JWT in Flask, you can use the create_access_token() function from the pyjwt.contrib.flask_jwt_extended module.

from flask_jwt_extended import create_access_token
from datetime import timedelta

def create_token(user_id):
    expires = timedelta(hours=1)
    token = create_access_token(identity=user_id, expires_delta=expires)
    return token

This function takes the user's ID and generates a JWT with an expiry time of 1 hour.

Verifying JWTs

To verify a JWT in Flask, you can use the verify_jwt_in_request() function from the pyjwt.contrib.flask_jwt_extended module.

from flask_jwt_extended import verify_jwt_in_request

def verify_token():
    token = request.headers.get('Authorization').split(" ")[1]
    try:
        verify_jwt_in_request(token)
    except:
        return jsonify(msg='Bad token'), 401

This function extracts the JWT from the Authorization header and verifies it. If the token is invalid or expired, it returns a 401 Unauthorized response.

Real-World Applications

JWTs are widely used in the following real-world applications:

Authentication: JWTs can be used to authenticate users on websites and APIs.
Authorization: JWTs can be used to grant access to specific resources or endpoints based on the user's role or permissions.
Email Verification: JWTs can be used to send email verification links to users.

Complete Code Implementation

Here's a complete example of using Flask-JWT-Extended for authentication and authorization:

from flask import Flask
from flask_jwt_extended import JWTManager, jwt_required, create_access_token

app = Flask(__name__)

# Configuring JWT settings
app.config['JWT_SECRET_KEY'] = 'your_secret_key'

jwt = JWTManager(app)

@app.route('/login', methods=["POST"])
def login():
    if user_exists(request.form.get('username'), request.form.get('password')):
        token = create_access_token(identity=request.form.get('username'))
        return jsonify(access_token=token)
    return jsonify(msg='Invalid credentials'), 401

@app.route('/protected', methods=["GET"])
@jwt_required
def protected():
    current_user = get_jwt_identity()
    return jsonify(msg='Welcome %s' % current_user)

Conclusion

By using pyjwt with Flask, you can add a layer of security to your web application by authenticating and authorizing users using JWTs.

OpenID Connect (OIDC)

OIDC is a protocol that allows users to sign in to a website without having to create an account on the website. Instead, users can sign in using their existing credentials from a trusted identity provider (IdP), such as Google or Facebook.

How it Works

The user visits the website and clicks on the "Sign In" button.
The website redirects the user to the IdP's login page.
The user enters their credentials and signs in.
The IdP sends the website an authentication token.
The website uses the authentication token to verify the user's identity and create a session for the user.

Benefits of OIDC

Simplified user experience: Users don't have to create and remember multiple passwords.
Increased security: OIDC uses strong authentication mechanisms to protect user accounts from unauthorized access.
Reduced development costs: Websites don't have to develop and maintain their own authentication systems.

Real-World Applications

E-commerce: OIDC can be used to allow customers to sign in to online stores using their existing social media accounts.
Social networking: OIDC can be used to allow users to sign in to social networking websites using their existing email addresses or phone numbers.
Enterprise applications: OIDC can be used to allow employees to sign in to enterprise applications using their corporate credentials.

Code Implementation

The following Python code snippet shows how to use the PyJWT library to create an OIDC authentication token:

import jwt

# Create a JWT token
token = jwt.encode(
    {
        "iss": "your-issuer",
        "sub": "your-subject",
        "aud": "your-audience",
        "iat": datetime.now(tz=timezone.utc),
        "exp": datetime.now(tz=timezone.utc) + timedelta(seconds=60),
    },
    "your-secret",
    algorithm="HS256",
)

# Send the token to the IdP

The following Python code snippet shows how to use the PyJWT library to verify an OIDC authentication token:

import jwt

# Verify a JWT token
token = jwt.decode(
    "your-token",
    "your-secret",
    algorithms=["HS256"],
)

Token decoding

PyJWT Token Decoding

What is JWT?

Think of a JWT (JSON Web Token) like a secret letter with three parts: a header, a payload, and a signature. The header contains information about the token, like what algorithm was used to create it. The payload is the actual data you want to send, like a username or email address. The signature is like a secret code that proves the token is valid.

Why decode a JWT?

You might need to decode a JWT to get the data inside it. For example, if you have a website that uses JWTs to authenticate users, you'll need to decode the JWT to get the user's identity.

How to decode a JWT

First, you need a library that can decode JWTs. PyJWT is a popular library for this.

Once you have the library, you can use the decode() method to decode a JWT. The decode() method takes the JWT as a string and a secret key as parameters. The secret key is used to verify the signature of the JWT.

import jwt

token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"
secret_key = "my_secret_key"

decoded_token = jwt.decode(token, secret_key, algorithms=["HS256"])

print(decoded_token)

The output of the decode() method is a dictionary containing the data from the payload of the JWT. In this example, the decoded token contains the following data:

{'sub': '1234567890', 'name': 'John Doe', 'iat': 1516239022}

Potential applications

JWTs are used in a variety of applications, including:

Authentication: JWTs can be used to authenticate users to a website or API.
Authorization: JWTs can be used to authorize users to access specific resources.
Data exchange: JWTs can be used to exchange data between two parties.

Conclusion

Decoding JWTs is a relatively simple process. By following the steps outlined in this guide, you can easily decode JWTs and access the data they contain.

Custom claims

Custom Claims

Custom claims allow you to add additional information to a JWT beyond the standard claims. This information can be used to customize the authorization or authentication process.

Issuing Custom Claims

To issue custom claims, you can use the claims argument to the encode() method. The claims argument is a dictionary where the keys are the claim names and the values are the claim values.

import jwt

claims = {
    "name": "John Doe",
    "email": "john.doe@example.com",
    "admin": True,
}

token = jwt.encode(claims, "secret", algorithm="HS256")

Decoding Custom Claims

To decode custom claims, you can use the get() method of the decoded JWT. The get() method takes the claim name as its first argument and returns the claim value.

import jwt

token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJuYW1lIjoiSm9obiBEb2UiLCJlbWFpbCI6ImpvaG4uZG9lQGV4YW1wbGUuY29tIiwiYWRtaW4iOnRydWV9.TJVA95OrM7E2cBab30RMHrHDcEfxjoYZgeFONFh7HgQ"

decoded_jwt = jwt.decode(token, "secret", algorithm="HS256")

name = decoded_jwt.get("name")
email = decoded_jwt.get("email")
admin = decoded_jwt.get("admin")

print(name)  # John Doe
print(email)  # john.doe@example.com
print(admin)  # True

Applications

Custom claims can be used in a variety of applications, including:

Authorization: Custom claims can be used to grant or deny access to specific resources. For example, you could issue a custom claim that grants access to a particular page on your website.
Authentication: Custom claims can be used to store additional information about the user, such as their name, email address, or role. This information can be used to personalize the user experience or to provide additional security.
Data Exchange: Custom claims can be used to exchange data between different applications. For example, you could issue a custom claim that contains a user's profile information and share it with another application.

Expiry handling

Expiry Handling in pyjwt

When creating a JWT, you can specify an expiration time for it. This means that the JWT will only be valid for a certain amount of time after it is issued.

How to Set an Expiration Time

To set an expiration time for a JWT, you use the expires_at argument when creating the token. The value of this argument should be a timestamp representing when the token should expire.

import jwt
import datetime

# Create a JWT that expires in 1 hour
token = jwt.encode(
    {"username": "alice"},
    "secret",
    algorithm="HS256",
    expires_at=datetime.datetime.utcnow() + datetime.timedelta(hours=1),
)

How to Validate an Expiration Time

When you receive a JWT, you can validate the expiration time to make sure it is still valid. To do this, you use the decode function and pass in the verify_expires argument.

import jwt

# Decode a JWT and validate the expiration time
token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ1c2VybmFtZSI6ImFsaWNlIn0.x5TvXg7_4RI97ZNrf6v-1vZvC7v0Ac_zyFudk23N6Aw"
decoded_token = jwt.decode(token, "secret", algorithms=["HS256"], verify_expires=True)

If the JWT is expired, the decode function will raise an ExpiredSignatureError exception.

Applications in the Real World

JWTs are used in a variety of applications where it is important to ensure that tokens are not used after they expire. Some common examples include:

Authentication: JWTs can be used to authenticate users to a web application. The JWT can contain information about the user's identity and permissions, and can be used to grant access to restricted resources.
Authorization: JWTs can be used to authorize users to perform specific actions. For example, a JWT could be used to authorize a user to access a particular file or folder.
Data exchange: JWTs can be used to securely exchange data between two parties. The JWT can contain the data that needs to be exchanged, and can be used to ensure that the data is not tampered with.

Token creation

Token Creation in JWT (JSON Web Tokens)

Simplified Explanation:

Imagine you have a special box that contains a message. You want to give this box to someone and ensure that:

They know that the message came from you.
They can't change the message without you knowing.
They can verify that the message hasn't been tampered with.

JWT is like that box. It uses three parts: a header, a payload, and a signature.

Header:

Contains information about the type of token and the method used to sign it.
For example: "Header: {alg: HS256, typ: JWT}"

Payload:

Contains the actual data you want to convey.
Can include claims like:
- "Name: John Doe"
- "Email: john.doe@example.com"

Signature:

A unique string that verifies the authenticity of the token.
Created by combining the header, payload, and a secret key that only you know.

Example:

import jwt
from datetime import datetime

# Create a dictionary for the payload
payload = {
    "name": "John Doe",
    "email": "john.doe@example.com",
    "exp": datetime.utcnow() + datetime.timedelta(minutes=5)  # Set expiration time
}

# Create the token using the secret key. The secret key should be a secure string.
token = jwt.encode(payload, "s3cret")

# Print the token
print(token)

Code Output:

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1lIjoiSm9obiBEb2UiLCJlbWFpbCI6ImpvaG4uZG9lQGV4YW1wbGUuY29tIiwiaWF0IjoxNjU0MTE1MTMyLCJleHAiOjE2NTQxMTU4MzJ9.O3xY-q09Gk48p7d3iK-aE80pwSqGiZOOE_DKArV68KI

Real-World Applications:

User Authentication: Generate tokens to identify users without storing passwords.
Authorization: Grant access to specific resources based on token claims.
Data Exchange: Securely share data between different systems using tokens.

Token encryption

Token Encryption

Imagine you have a secret box with a special lock. You can put valuable items in the box and lock it with the key. Now, only someone who has the key can open the box and retrieve the contents.

In the world of cryptography, tokens are like the secret boxes. They contain sensitive information that needs to be protected. Encryption is the "key" that protects the contents of tokens by making them unreadable to unauthorized parties.

Types of Encryption

Symmetric encryption: Uses a single key to encrypt and decrypt data. If you have the key, you can both read and write the data.
Asymmetric encryption: Uses two different keys – a public key and a private key. The public key is used to encrypt data, while the private key is used to decrypt it.

How Token Encryption Works

For token encryption with PyJWT, you first initialize an algorithm and key. The algorithm determines how the encryption will be performed. Then, you use the encrypt() function to encrypt the token.

Here's an example:

import jwt

algorithm = "HS256"
secret_key = "my_secret_key"

token = jwt.encode({"data": "secret_data"}, secret_key, algorithm=algorithm)

# The encrypted token will be stored in the 'token' variable.

Applications

Token encryption is used in many applications:

Secure data transfer: Encrypting tokens ensures that sensitive data is protected during transmission.
Authentication and authorization: Tokens can be used to store user information and grant permissions to access resources. By encrypting tokens, you prevent unauthorized access.
Online transactions: Encryption protects financial information during online payments and other transactions.

Real-World Example

Imagine a website that allows users to purchase products. When a user logs in, the server generates an encrypted token containing the user's ID and other information. This token is used for subsequent interactions with the website, ensuring the user's identity and permissions are verified securely.

Token storage

Token Storage

What is a Token?

Imagine a token as a special password that gives you access to something. Just like you need a password to unlock your phone, a token is needed to access certain websites or apps.

Token Storage

Storing tokens securely is like keeping your secrets safe. There are three main ways to store tokens:

1. Cookies

Cookies are like little notes that your browser stores. When you visit a website, the website can give you a cookie that remembers who you are and what you did. Tokens can be stored in cookies, so when you come back to the website, it knows who you are.

Pros:

Easy to use
Doesn't require any special setup

Cons:

Not very secure (cookies can be stolen)
Limited storage space

2. Local Storage

Local storage is a space in your browser that stores data locally on your computer. Tokens can be stored here, so you don't have to keep entering them every time you visit a website.

Pros:

More secure than cookies
Persistent (data is saved even after you close your browser)

Cons:

Limited storage space
Not available in all browsers

3. Custom Storage

You can also create your own custom storage mechanism for tokens. This gives you complete control over how tokens are stored and retrieved.

Pros:

Most secure option
Highly customizable

Cons:

Requires more setup and maintenance

Real-World Examples

Websites: Websites that allow you to stay logged in (e.g., Facebook, Amazon) use tokens stored in cookies.
Mobile apps: Apps that store user preferences or authentication details use tokens stored locally on your phone.
APIs: Web services that require authentication often use tokens to grant access to certain resources.

Code Examples

Storing a Token in a Cookie:

import jwt

token = jwt.encode({"username": "admin"}, "my-secret")

# Create a cookie and set its value to the token
cookie = http.cookiejar.Cookie(
    version=0,
    name="access_token",
    value=token,
    path="/",
    secure=True,
    httponly=True,
)

# Add the cookie to the request headers
headers = {
    "Cookie": cookie.output(header="", sep="; ")
}

Storing a Token in Local Storage:

import localstorage

# Create a local storage instance
storage = localstorage.LocalStorage()

# Store the token in local storage
storage["access_token"] = token

Retrieving a Token from Custom Storage:

# Define a function to retrieve the token
def get_token():
    # Read the token from a file or database
    with open("access_token.txt", "r") as f:
        token = f.read()
    return token

Potential Applications

User authentication: Tokens can be used to authenticate users on websites and apps.
Resource access control: Tokens can be used to grant access to specific resources based on user permissions.
Session management: Tokens can be used to keep track of user sessions and maintain their state.

JWT (JSON Web Tokens)

What are JWTs?

Imagine you have a secret box that can store important information. This secret box is called a JSON Web Token (JWT). JWTs are used to securely pass information between two parties, like when you log in to a website or make a purchase online.

Parts of a JWT

JWTs have three main parts, like a sandwich:

Header: This is the top part of the sandwich. It contains information about the JWT, like its type and the algorithm used to create it.
Payload: This is the middle part of the sandwich. It contains the actual information you want to pass, like your username or the products you want to buy.
Signature: This is the bottom part of the sandwich. It's created by combining the header and payload with a secret key. The signature ensures that the JWT hasn't been tampered with.

Example

Here's a simplified example of a JWT:

header: {
    alg: "HS256"
}
payload: {
    username: "example",
    email: "example@example.com"
}
signature: "ASDF1234"

Creating JWTs

To create a JWT, you use a library like pyjwt. Here's an example:

import jwt

token = jwt.encode(
    {"username": "example"},
    "secret_key",
    algorithm="HS256"
)

Verifying JWTs

To verify a JWT, you also use a library like pyjwt. Here's an example:

import jwt

token = "ASDF1234"

decoded_token = jwt.decode(token, "secret_key", algorithms=["HS256"])

print(decoded_token["username"])  # Output: "example"

Applications

JWTs are used in a variety of real-world applications, including:

Authentication: JWTs can be used to authenticate users on websites and APIs.
Authorization: JWTs can be used to determine what actions a user is authorized to perform.
Data Exchange: JWTs can be used to securely exchange information between different parties.

Integration with authentication systems

Integration with Authentication Systems

1. JWTs for User Authentication

JWTs can be used to authenticate users.
When a user logs in, the server generates a JWT containing the user's ID and other relevant data.
The JWT is then sent to the user's client, typically within an HTTP response.
The client stores the JWT and includes it in all subsequent requests to the server.
The server verifies the JWT and allows the user access to protected resources.

Implementation:

from flask import Flask, request, jsonify
from jwt import encode, decode

# Create a Flask app
app = Flask(__name__)

# Secret key for JWT creation and verification
SECRET_KEY = 'mysecretkey'

# Route for user login
@app.route('/login', methods=['POST'])
def login():
    # Get the user's username and password
    username = request.form.get('username')
    password = request.form.get('password')

    # Check if the username and password are correct
    if username == 'admin' and password == 'admin':
        # Generate a JWT with the user's ID
        jwt = encode({'id': 1}, SECRET_KEY, algorithm='HS256')

        # Return the JWT to the client
        return jsonify({'jwt': jwt})

    # If the username and password are incorrect, return an error
    return jsonify({'error': 'Invalid credentials'}), 401

# Route for protected resources
@app.route('/protected', methods=['GET'])
def protected():
    # Get the JWT from the request header
    jwt = request.headers.get('Authorization')

    # Verify the JWT
    try:
        data = decode(jwt, SECRET_KEY, algorithms=['HS256'])
    except:
        return jsonify({'error': 'Invalid JWT'}), 401

    # Return the protected resource
    return jsonify({'message': 'Welcome!'})

# Run the app
app.run(debug=True)

Potential Application:

User authentication in web applications, mobile apps, or APIs.

2. JWTs for API Authorization

JWTs can be used to authorize API requests.
When a client makes an API request, it includes a JWT in the request header.
The API server verifies the JWT and allows the client access to the requested resource.

Implementation:

import requests

# API URL
API_URL = 'https://api.example.com'

# JWT
JWT = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c'

# Make an API request
response = requests.get(API_URL, headers={'Authorization': 'Bearer ' + JWT})

# Print the response
print(response.text)

Potential Application:

Authorization of API requests from mobile apps, web applications, or other services.

3. JWTs for Single Sign-On (SSO)

JWTs can be used to implement SSO.
A user logs in to a central authentication service (CAS).
The CAS generates a JWT and returns it to the user's browser.
The user's browser forwards the JWT to all other applications that need to authenticate the user.
The applications verify the JWT and allow the user access.

Implementation:

# CAS URL
CAS_URL = 'https://cas.example.com'

# JWT
JWT = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c'

# CAS login URL
LOGIN_URL = CAS_URL + '/login?service='

# CAS logout URL
LOGOUT_URL = CAS_URL + '/logout'

# Redirect the user to the CAS login page
@app.route('/login')
def login():
    return redirect(LOGIN_URL)

# Redirect the user to the CAS logout page
@app.route('/logout')
def logout():
    return redirect(LOGOUT_URL)

# Process the CAS login response
@app.route('/cas/callback')
def callback():
    # Get the JWT from the CAS response
    jwt = request.args.get('ticket')

    # Verify the JWT
    try:
        data = decode(jwt, SECRET_KEY, algorithms=['HS256'])
    except:
        return jsonify({'error': 'Invalid JWT'}), 401

    # Log the user in
    login_user(data['id'], remember=True)

    # Redirect the user to the application home page
    return redirect(url_for('home'))

Potential Application:

SSO for multiple applications within an organization.

Token validation

Token Validation

What is Token Validation?

Imagine you have a secret password that you share with your best friend. If your friend sends you a message using that password, you know it's really from them. In the same way, tokens are used to validate that a message came from the person who sent it.

How Token Validation Works

When you create a token, you include some information in it, like your name and when the token expires. When someone receives the token, they can check if the information inside matches what they know about you. If it does, they can be sure the token is valid.

Steps in Token Validation:

Decoding: The token is converted into its original form.
Signature Verification: The token's signature is checked to make sure it matches the one created by the sender.
Claims Validation: The claims inside the token are checked to see if they are valid. For example, the token might expire after a certain time, so the validator checks if that time has passed.
Payload Validation: The payload (the data inside the token) is checked to make sure it hasn't been tampered with.

Real-World Applications

Authentication: Tokens can be used to verify the identity of users accessing a website or application.
Authorization: Tokens can be used to grant access to certain resources or actions based on the user's role or permissions.
Data Protection: Tokens can be used to encrypt sensitive data, preventing unauthorized access.

Code Example

import jwt

# The token to be validated
token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"

# The secret key used to create the token
secret_key = "my_super_secret_key"

# Decode the token
decoded_token = jwt.decode(token, secret_key, algorithms=["HS256"])

# Print the decoded token
print(decoded_token)

Output:

{'sub': '1234567890', 'name': 'John Doe', 'iat': 1516239022}

Single sign-on (SSO)

Single Sign-On (SSO) with PyJWT

What is SSO?

Imagine you have a lot of websites, like Facebook, Google, and Amazon. Each website has its own login page where you have to enter your username and password. This can be annoying, especially if you have to log in to multiple websites frequently.

SSO makes it easier. It allows you to log in once to a central service, and then you can access all the websites that use that service without having to log in again. It's like having a single key that unlocks all the doors in your house.

How Does PyJWT Enable SSO?

PyJWT is a library that helps you create and verify JSON Web Tokens (JWTs). JWTs are used in SSO to securely pass information about a user from one website to another.

When you log in to a website that uses PyJWT for SSO, the website creates a JWT that contains information about you, such as your name, email, and permissions. This JWT is then passed to the SSO service, which verifies the JWT and grants you access to the other websites that use that service.

Example Implementation

# Create a JWT for a user
import jwt

user_info = {
    "name": "John Doe",
    "email": "john.doe@example.com",
    "permissions": ["read", "write"]
}

jwt_token = jwt.encode(user_info, "secret", algorithm="HS256")

# Pass the JWT to the SSO service
sso_service.verify_and_grant_access(jwt_token)

Real-World Applications

SSO is used by many large organizations, including Google, Microsoft, and Amazon. It makes it easier for employees to access multiple applications and services without having to remember multiple passwords.

Potential Applications

Enterprise applications: SSO can be used to streamline access to enterprise applications, such as CRM, ERP, and HR systems.
E-commerce: SSO can be used to allow customers to log in to multiple e-commerce websites using a single account.
Social media: SSO can be used to allow users to log in to multiple social media websites using a single account.

Cross-origin authentication

Cross-Origin Authentication

Imagine you have two websites: website A and website B. You want users to be able to access both websites without having to log in twice. You can achieve this using cross-origin authentication.

1. JSON Web Tokens (JWT)

A JWT is a secure way to pass information between two different websites. It's a small, self-contained token that contains data about the user, such as their username and permissions.

How it Works:

Website A creates a JWT for the user.
Website A sends the JWT to the user's browser.
The user's browser stores the JWT.
When the user visits website B, the browser sends the JWT to website B.
Website B validates the JWT and grants the user access to the website.

2. Cross-Origin Resource Sharing (CORS)

CORS is a security mechanism that allows websites to make requests to other websites in different domains. Without CORS, browsers would not allow cross-origin requests for security reasons.

How it Works:

Website A makes a cross-origin request to website B.
Website B responds with a CORS header that allows the request.
Website A receives the response and can now access the data from website B.

Real-World Example:

A common use case for cross-origin authentication is single sign-on (SSO). SSO allows users to log in once and access multiple websites without having to log in each time.

Code Implementation (simplified):

Website A (Creates JWT):

import jwt

payload = {"username": "alice", "role": "admin"}
token = jwt.encode(payload, "secretkey", algorithm="HS256")

Website B (Validates JWT):

import jwt

token = request.headers["Authorization"]
payload = jwt.decode(token, "secretkey", algorithms=["HS256"])

Potential Applications:

SSO
Federated identity management
Social media logins
Authentication for microservices

Compatibility with other JWT libraries

Compatibility with Other JWT Libraries

Summary:

JWT libraries allow you to create and verify JSON Web Tokens (JWTs) securely. PyJWT is a popular JWT library in Python, and it's compatible with many other JWT libraries to ensure interoperability.

Topics:

1. Interoperability:

PyJWT can create and verify tokens compliant with the JWT standard, which means they can be used with other JWT libraries.
This allows you to seamlessly exchange JWTs between applications that use different libraries.

2. Algorithm Support:

PyJWT supports a wide range of signing algorithms, including RS256, HS256, and ES256.
This allows you to choose the algorithm that best suits your security requirements and is compatible with other libraries.

3. Token Format:

JWTs have a standardized format consisting of three parts: header, payload, and signature.
PyJWT follows this format, ensuring that the tokens it generates are compatible with other libraries.

Real-World Code Examples:

Creating a JWT with PyJWT:

import jwt

# Create a JWT
encoded_jwt = jwt.encode(
    {"user_id": 123},
    "secret_key",
    algorithm="HS256",
)

# Send or store the JWT
print(encoded_jwt)

Verifying a JWT with Another Library:

# Use another JWT library to verify the token
import jws

# Verify the JWT
decoded_jwt = jws.verify(encoded_jwt, "secret_key", algorithms=["HS256"])

# Get the data from the token
print(decoded_jwt.get("user_id"))

Potential Applications:

Authentication: JWTs can be used for user authentication, allowing users to access secure applications securely.
Authorization: JWTs can also be used to authorize users to perform specific actions within an application.
Data Exchange: JWTs can be used to securely exchange data between different systems or applications.

Header parameters

Header Parameters in pyjwt

The header of a JWT consists of three required parameters:

typ: Type of token, usually "JWT"
alg: Algorithm used to sign the token, such as "HS256" or "RS256"

Optional parameters include:

cty: Content type, usually "JWT"
kid: Key ID, used to specify which key to use for verification if multiple keys are available

Simplified Explanations:

typ: Tells the recipient that the token is a JWT, like a letter with a return address.
alg: Indicates how the token was signed, like a sealed envelope with the sender's signature.
cty: Specifies the format of the data inside the token, similar to a letter written in a specific language.
kid: If you have multiple keys, this helps the recipient identify the correct key to unlock the token.

Code Snippets:

# Header with required parameters
header = {"typ": "JWT", "alg": "HS256"}

# Header with optional parameters
header = {"typ": "JWT", "alg": "RS256", "cty": "JWT", "kid": "mykey"}

Real-World Implementations:

User Authentication: When a user logs in to an application, a JWT can be created with the header parameters indicating the token type and signing algorithm. This token is then used for subsequent requests to ensure the user is still authenticated.
Authorization: JWTs can be used to authorize access to resources by specifying the required permissions in the header parameters.
Data Exchange: JWTs can be used to securely exchange data between different systems or applications by specifying the content type in the header parameters.

Potential Applications:

Web authentication and authorization
API token-based access control
Single sign-on (SSO) systems
Secure data exchange between systems

Custom headers

Custom Headers in JWTs

What are JWT Headers?

JWTs (JSON Web Tokens) have three main parts: header, payload, and signature. The header contains information about how the JWT was created and how it should be used.

Custom Headers

In addition to the standard headers, you can also add your own custom headers. This can be useful for including information that is specific to your application.

Adding Custom Headers

To add a custom header, you use the header parameter when creating the JWT:

import jwt

header = {"my_custom_header": "my_custom_header_value"}
jwt_token = jwt.encode({"name": "John Doe"}, "secret", algorithm="HS256", headers=header)

Using Custom Headers

Once you have added a custom header, you can access its value like this:

import jwt

decoded_jwt = jwt.decode(jwt_token, "secret", algorithms=["HS256"])
custom_header_value = decoded_jwt.headers["my_custom_header"]

Real-World Applications

Storing user roles: You could store a user's role in a custom header, which would allow you to authorize them for different actions in your application.
Tracking application usage: You could use a custom header to track how often a JWT is used, which would help you identify any performance issues.
Passing additional metadata: You could use a custom header to pass any other information that you need to your application, such as a user's location or device type.

Example

Here's an example of a JWT with a custom header:

{
  "header": {
    "typ": "JWT",
    "my_custom_header": "my_custom_header_value"
  },
  "payload": {
    "name": "John Doe"
  },
  "signature": "xyz..."
}

When you decode this JWT, you would get the following results:

>>> import jwt
>>> decoded_jwt = jwt.decode(jwt_token, "secret", algorithms=["HS256"])
>>> decoded_jwt.headers
{'typ': 'JWT', 'my_custom_header': 'my_custom_header_value'}
>>> decoded_jwt.payload
{'name': 'John Doe'}

Secret key management

Secret Key Management in pyjwt

What is a secret key?

A secret key is a string of characters that is used to sign and verify JWTs. It must be kept secret, as anyone who knows the key can create or modify JWTs.

How to store secret keys

Secret keys should be stored in a secure location, such as a password manager or a hardware security module (HSM). They should never be stored in plain text in your code.

How to generate a secret key

You can generate a secret key using the following code:

import secrets

secret_key = secrets.token_urlsafe(32)

This will generate a 32-character secret key.

How to use a secret key

Once you have a secret key, you can use it to sign and verify JWTs.

To sign a JWT, you use the following code:

import jwt

token = jwt.encode({'some': 'data'}, secret_key, algorithm='HS256')

This will create a JWT that is signed with the secret key.

To verify a JWT, you use the following code:

import jwt

decoded = jwt.decode(token, secret_key, algorithms=['HS256'])

This will decode the JWT and return the original data.

Real-world applications

Secret key management is essential for any application that uses JWTs. It is used to protect the integrity and authenticity of JWTs, and to prevent unauthorized access to data.

Some real-world applications of secret key management include:

Authentication: JWTs can be used to authenticate users to a web application or API. The secret key is used to verify that the JWT was signed by a trusted party.
Authorization: JWTs can be used to authorize users to access specific resources. The secret key is used to verify that the JWT was signed by a trusted party and that the user has the necessary permissions.
Data exchange: JWTs can be used to exchange data between different applications or services. The secret key is used to verify that the JWT was signed by a trusted party and that the data has not been tampered with.

Usage with Django

JWTs with Django

What is a JWT?

A JWT (JSON Web Token) is a way to store information in a secure way. It's like a special box that contains your data.

How to use JWTs with Django:

To use JWTs with Django, you need to follow these steps:

Install the pyjwt package: This is the library that will help you create and decode JWTs.

pip install pyjwt

Create a secret key: This is a special password that will protect your JWTs.

SECRET_KEY = 'your_super_secret_key'

Encode a JWT: This is how you create a JWT. You put your data in the box and lock it with your secret key.

import jwt

data = {'username': 'john', 'email': 'john@example.com'}
token = jwt.encode(data, SECRET_KEY, algorithm='HS256')

Decode a JWT: This is how you get your data back from the JWT. You unlock the box using your secret key.

data = jwt.decode(token, SECRET_KEY, algorithms=['HS256'])

Real-world applications:

Authentication: You can use JWTs to keep track of who is logged in to your website or app.
Authorization: You can use JWTs to grant access to certain parts of your website or app.
Data sharing: You can use JWTs to securely share data between different systems.

Token expiration

Token Expiration

In PyJWT, tokens have an expiration time defined by the exp claim. This ensures that tokens are only valid for a certain period of time.

How it works

When creating a token, you can specify the expiration time using the expires_delta parameter. This parameter takes a timedelta object, which represents the amount of time the token should be valid for. For example:

import jwt
from datetime import timedelta

token = jwt.encode(
    {"some": "payload"},
    "secret",
    algorithm="HS256",
    expires_delta=timedelta(minutes=5),
)

This will create a token that is valid for 5 minutes.

To verify the expiration time of a token, you can use the decode function:

import jwt
from datetime import datetime

token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzb21lIjoicGF5bG9hZCIsImV4cCI6MTU5NjU2Njg1Mn0.R3XHzf6F1m7mqpuqq_9h0_5qhDPIiwwgL9Fcdnur4mY"
decoded_token = jwt.decode(token, "secret", algorithms=["HS256"])

expiration_time = datetime.fromtimestamp(decoded_token["exp"])
print(expiration_time)

This will print the expiration time of the token, which will be 5 minutes from the time the token was created.

Applications

Token expiration is used in a variety of applications, including:

Authentication: Tokens can be used to authenticate users to a service. By setting the expiration time of the token, you can ensure that the token is only valid for a certain period of time, preventing unauthorized access to the service.
Authorization: Tokens can be used to authorize users to perform certain actions. By setting the expiration time of the token, you can ensure that the token is only valid for a certain period of time, preventing unauthorized actions from being performed.
Data protection: Tokens can be used to encrypt sensitive data. By setting the expiration time of the token, you can ensure that the data is only accessible for a certain period of time, protecting it from unauthorized access.

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