# javax.crypto.spec

***

**1. Generating a SecretKeySpec for AES-256 encryption**

```java
import javax.crypto.spec.SecretKeySpec;

byte[] key = "mySecretKey".getBytes("UTF-8");
SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");
```

**2. Generating an IvParameterSpec for CBC mode encryption**

```java
import javax.crypto.spec.IvParameterSpec;

byte[] iv = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F };
IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
```

**3. Generating a PBEKeySpec for password-based encryption**

```java
import javax.crypto.spec.PBEKeySpec;
import java.util.Arrays;

char[] password = "myPassword".toCharArray();
byte[] salt = "mySalt".getBytes("UTF-8");
int iterations = 1000;
PBEKeySpec pbeKeySpec = new PBEKeySpec(password, salt, iterations, 256);
```

**4. Generating a DHParameterSpec for Diffie-Hellman key exchange**

```java
import javax.crypto.spec.DHParameterSpec;
import java.math.BigInteger;

BigInteger p = new BigInteger("FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A63A3620FFFFFFFFFFFFFFFF", 16);
BigInteger g = new BigInteger("2", 16);
DHParameterSpec dhParameterSpec = new DHParameterSpec(p, g);
```

**5. Generating an EllipticCurveSpec for ECDSA signature verification**

```java
import javax.crypto.spec.EllipticCurveSpec;
import java.math.BigInteger;

BigInteger a = new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F", 16);
BigInteger b = new BigInteger("0", 16);
BigInteger p = new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFFFFFFFFFFFF", 16);
EllipticCurveSpec ellipticCurveSpec = new EllipticCurveSpec(p, a, b);
```

**6. Generating an OAEPParameterSpec for OAEP padding**

```java
import javax.crypto.spec.OAEPParameterSpec;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

MessageDigest digest = MessageDigest.getInstance("SHA-256");
OAEPParameterSpec oaepParameterSpec = new OAEPParameterSpec("SHA-256", "MGF1", digest, MGFParameters.SHA256);
```

**7. Generating a PBEParameterSpec for PBE encryption**

```java
import javax.crypto.spec.PBEParameterSpec;

int iterationCount = 1000;
byte[] salt = "mySalt".getBytes("UTF-8");
PBEParameterSpec pbeParameterSpec = new PBEParameterSpec(salt, iterationCount);
```

**8. Generating an RSAPrivateKeySpec for RSA decryption**

```java
import javax.crypto.spec.RSAPrivateKeySpec;
import java.math.BigInteger;

BigInteger modulus = new BigInteger("10001", 16);
BigInteger exponent = new BigInteger("65537", 16);
RSAPrivateKeySpec rsaPrivateKeySpec = new RSAPrivateKeySpec(modulus, exponent);
```

**9. Generating an RSAPublicKeySpec for RSA encryption**

```java
import javax.crypto.spec.RSAPublicKeySpec;
import java.math.BigInteger;

BigInteger modulus = new BigInteger("10001", 16);
BigInteger exponent = new BigInteger("65537", 16);
RSAPublicKeySpec rsaPublicKeySpec = new RSAPublicKeySpec(modulus, exponent);
```

**10. Generating an X509EncodedKeySpec for X.509 certificate decoding**

```java
import javax.crypto.spec.X509EncodedKeySpec;
import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;

Certificate certificate = CertificateFactory.getInstance("X.509").generateCertificate(new FileInputStream("certificate.crt"));
X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(certificate.getEncoded());
```

**11. Generating a Cipher for AES-256 encryption in CBC mode with PKCS5 padding**

```java
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

byte[] key = "mySecretKey".getBytes("UTF-8");
byte[] iv = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F };
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "AES"), new IvParameterSpec(iv));
```

**12. Generating a Cipher for AES-256 decryption in CBC mode with PKCS5 padding**

```java
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

byte[] key = "mySecretKey".getBytes("UTF-8");
byte[] iv = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F };
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key, "AES"), new IvParameterSpec(iv));
```

**13. Generating a Cipher for AES-256 encryption in ECB mode with PKCS5 padding**

```java
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

byte[] key = "mySecretKey".getBytes("UTF-8");
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "AES"));
```

**14. Generating a Cipher for AES-256 decryption in ECB mode with PKCS5 padding**

```java
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

byte[] key = "mySecretKey".getBytes("UTF-8");
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key, "AES"));
```

**15. Generating a Cipher for AES-256 encryption in CFB mode with PKCS5 padding**

```java
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

byte[] key = "mySecretKey".getBytes("UTF-8");
byte[] iv = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F };
Cipher cipher = Cipher.getInstance("AES/CFB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "AES"), new IvParameterSpec(iv));
```

**16. Generating a Cipher for AES-256 decryption in CFB mode with PKCS5 padding**

```java
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

byte[] key = "mySecretKey".getBytes("UTF-8");
byte[] iv = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F };
Cipher cipher = Cipher.getInstance("AES/CFB/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key, "AES"), new IvParameterSpec(iv));
```

**17. Generating a Cipher for AES-256 encryption in OFB mode with PKCS5 padding**

```java
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

byte[] key = "mySecretKey".getBytes("UTF-8");
byte[] iv = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F };
Cipher cipher = Cipher.getInstance("AES/OFB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "AES"), new IvParameterSpec(iv));
```

**18. Generating a Cipher for AES-256 decryption in OFB mode with PKCS5 padding**

```java
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

byte[] key = "mySecretKey".getBytes("UTF-8");
byte[] iv = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F };
Cipher cipher = Cipher.getInstance("AES/OFB/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key, "AES"), new IvParameterSpec(iv));
```

**19. Generating a Cipher for AES-256 encryption in CTR mode**

```java
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

byte[] key = "mySecretKey".getBytes("UTF-8");
byte[] iv = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F };
Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "AES"), new IvParameterSpec(iv));
```

**20. Generating a Cipher for AES-256 decryption in CTR mode**

```java
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

byte[] key = "mySecretKey".getBytes("UTF-8");
byte[] iv = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F };
Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding");
cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key, "AES"), new IvParameterSpec(iv));
```

**21. Generating a Cipher for AES-256 encryption in GCM mode**

```java
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;

```