de.flexiprovider.core.kdf
Class KDF2

java.lang.Object
  |
  +--de.flexiprovider.api.KeyDerivation
        |
        +--de.flexiprovider.core.kdf.KDF2

public class KDF2

extends KeyDerivation

KDF2 is a key derivation function descriped in IEEE 1363a-2004. It is based on the constructions given in ANSI X9.42:2001 and X9.63.

KDF2 can be used as follows:

 KeyDerivation kdf = Registry.getKeyDerivation("KDF2");
 kdf.init(secretKey.toByteArray());
 kdf.setSharedInfo(sharedInfo.toByteArray());
 byte[] derivedKey = kdf.doFinal(int keyDataLen);
 

Author:

Jochen Hechler, Marcus Stögbauer, Martin Döring

Constructor Summary

KDF2()
Constructor.

Method Summary

byte[]	deriveKey(int keySize) This function does the actual key derivation.
void	init(byte[] secret, AlgorithmParameterSpec params) Initialize the KDF with a secret and parameters.

Methods inherited from class java.lang.Object

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

Constructor Detail

KDF2

public KDF2()

Constructor. Set the message digest.

Method Detail

init

public void init(byte[] secret,
                 AlgorithmParameterSpec params)
          throws InvalidKeyException,
                 InvalidAlgorithmParameterException

Initialize the KDF with a secret and parameters. The parameters have to be null or an instance of KDFParameterSpec.

Overrides:

init in class KeyDerivation

Parameters:

secret - the secret from which to derive the key

params - the parameters

Throws:

InvalidKeyException - if the secret is null.

InvalidAlgorithmParameterException - if the parameters are not null and not an instance of KDFParameterSpec.

deriveKey

public byte[] deriveKey(int keySize)

This function does the actual key derivation. It uses the shared key value z and the given key size, with the desired hash function H and the optional SharedInfo and computes

 Hash(i) = H(Z || counter || [SharedInfo])
 

where the counter is a 32-bit string. The counter is increased by one in for every round.

Overrides:

deriveKey in class KeyDerivation

Parameters:

keySize - the desired length of the derived key

Returns:

the derived key with the specified length, or null if the key size is < 0.