iaik.pkcs.pkcs5

Class PBKDF2

java.lang.Object

javax.crypto.KeyGeneratorSpi

iaik.pkcs.pkcs5.PBKDF2

Direct Known Subclasses:

PBKDF2.PBKDF2WithHmacSHA1, PBKDF2.PBKDF2WithHmacSHA224, PBKDF2.PBKDF2WithHmacSHA256, PBKDF2.PBKDF2WithHmacSHA384, PBKDF2.PBKDF2WithHmacSHA512

public class PBKDF2
extends javax.crypto.KeyGeneratorSpi

This class implements a KeyGenerator for the PBKDF2 (password-based-key-derivation-function-2) specified by the PKCS#5 v2.1 Password-Based Cryptography Standard to derive a key from a password.

The PBKDF2 key derivation function PBKDF2 needs the following parameters: salt value, iteration count, length of the to-be-derived key, and (MAC based) pseudo random function (default: HMCA/SHA1). After creating a PBKDF2 KeyGenerator you have to specify salt value, iteration count and length of the to-be-derived key as PBEKeyAndParameterSpec object. If you want to use another pseudorandom function than HMAC/SHA1 you may use a PBKDF2KeyAndParameterSpec object allowing to specify an alternative mac function by its AlgorithmID. Both parameter classes also need the (encoded) password from which to derive the secret key.

The following example uses the PBKDF2 KeyGenerator to derive an AES key from a password:

 char[] password = { 't', 'o', 'p', 'S', 'e', 'c', 'r', 'e', 't' };
 // create a KeySpec from our password
 PBEKeySpec keySpec = new PBEKeySpec(password);
 // use the "PKCS#5" or "PBE" SecretKeyFactory to convert the password
 SecretKeyFactory kf = SecretKeyFactory.getInstance("PKCS#5", "IAIK");
 // create an appropriate PbeKey
 PBEKey pbeKey = (PBEKey)kf.generateSecret(keySpec);
 // create PBKDF2 KeyGenerator 
 KeyGenerator pbkdf2 = KeyGenerator.getInstance("PBKDF2", "IAIK");
 int iterationCount = 2000;
 byte[] salt = 32;
 SecureRandom random = ...;
 random.nextBytes(salt);
 int derivedKeyLength = 16;
 PBEKeyAndParameterSpec parameterSpec =
   new PBEKeyAndParameterSpec(pbeKey.getEncoded(),
                              salt,
                              iterationCount,
                              derivedKeyLength);
 
 pbkdf2.init(parameterSpec, random);
 SecretKey derivedKey = pbkdf2.generateKey();
 String keyName = "AES";
 // use SecretKeyFactory to set the right key format
 SecretKeySpec spec = new SecretKeySpec(derivedKey.getEncoded(), keyName);
 SecretKeyFactory kf = SecretKeyFactory.getInstance(keyName, "IAIK");
 SecretKey cipherKey = kf.generateSecret(spec);

 

As mentioned above you may use a PBKDF2KeyAndParameterSpec object to specify another (mac based) pseudo random function than the default HMAC/SHA1, e.g.:

 PBKDF2KeyAndParameterSpec parameterSpec =
   new PBKDF2KeyAndParameterSpec(pbeKey.getEncoded(),
                                 salt,
                                 iterationCount,
                                 derivedKeyLength);
 parameterSpec.setPrf((AlgorithmID)AlgorithmID.hMAC_SHA256.clone());                                
 

Alternatively you may use one of the following pre-defined PPKDF2 KeyGenerators with fixed pseudorandom function:

• PBKDF2WithHmacSHA1:
  PBKDF2 with HMAC/SHA1: KeyGenerator.getInstance("PBKDF2WithHmacSHA1", "IAIK");
  
• PBKDF2WithHmacSHA224:
  PBKDF2 with HMAC/SHA224: KeyGenerator.getInstance("PBKDF2WithHmacSHA224", "IAIK");
  
• PBKDF2WithHmacSHA256:
  PBKDF2 with HMAC/SHA256: KeyGenerator.getInstance("PBKDF2WithHmacSHA256", "IAIK");
  
• PBKDF2WithHmacSHA384:
  PBKDF2 with HMAC/SHA384: KeyGenerator.getInstance("PBKDF2WithHmacSHA384", "IAIK");
  
• PBKDF2WithHmacSHA512:
  PBKDF2 with HMAC/SHA512: KeyGenerator.getInstance("PBKDF2WithHmacSHA512", "IAIK");
  

Version:

File Revision 19

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PBKDF2.PBKDF2WithHmacSHA1 PBKDF2 key derivation function using HmacSHA1 as pseudo random function.
static class	PBKDF2.PBKDF2WithHmacSHA224 PBKDF2 key derivation function using HmacSHA224 as pseudo random function.
static class	PBKDF2.PBKDF2WithHmacSHA256 PBKDF2 key derivation function using HmacSHA256 as pseudo random function.
static class	PBKDF2.PBKDF2WithHmacSHA384 PBKDF2 key derivation function using HmacSHA384 as pseudo random function.
static class	PBKDF2.PBKDF2WithHmacSHA512 PBKDF2 key derivation function using HmacSHA512 as pseudo random function.

Constructor Summary

Constructors

Constructor and Description
PBKDF2() The default constructor

Method Summary

Methods

Modifier and Type	Method and Description
javax.crypto.SecretKey	engineGenerateKey() Derives symmetric key.
void	engineInit(java.security.spec.AlgorithmParameterSpec algorithmParameterSp, java.security.SecureRandom secureRandom) Initializes the password-based-key-derivation-function
void	engineInit(int int1, java.security.SecureRandom secureRandom) Don't use this method.
void	engineInit(java.security.SecureRandom secureRandom) Don't use this method.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PBKDF2

public PBKDF2()

The default constructor

Method Detail

engineGenerateKey

public javax.crypto.SecretKey engineGenerateKey()

Derives symmetric key. The algorithm name is set to "RAW" and may be later changed by the calling application, if required:

 String algorithm = ...;
 KeyGenerator pbkdf2 = KeyGenerator.getInstance("PBKDF2", "IAIK");
 ...
 iaik.security.cipher.SecretKey secretKey = (iaik.security.cipher.SecretKey)pbkdf2.generateKey();
 secretKey.setAlgorithm(algorithm);
 

Specified by:

engineGenerateKey in class javax.crypto.KeyGeneratorSpi

Returns:

the derived key

engineInit

public void engineInit(int int1,
              java.security.SecureRandom secureRandom)

Don't use this method. It is not implemented.

Specified by:

engineInit in class javax.crypto.KeyGeneratorSpi

engineInit

public void engineInit(java.security.SecureRandom secureRandom)

Don't use this method. It is not implemented.

Specified by:

engineInit in class javax.crypto.KeyGeneratorSpi

engineInit

public void engineInit(java.security.spec.AlgorithmParameterSpec algorithmParameterSp,
              java.security.SecureRandom secureRandom)
                throws java.security.InvalidAlgorithmParameterException

Initializes the password-based-key-derivation-function

Specified by:

engineInit in class javax.crypto.KeyGeneratorSpi

Parameters:

algorithmParameterSp - must be an instance of PBEKeyAndParameterSpec

secureRandom - not needed, should be null

Throws:

java.security.InvalidAlgorithmParameterException