de.flexiprovider.core.elgamal.semanticallysecure
Class SSVElGamal

java.lang.Object
  |
  +--javax.crypto.CipherSpi
        |
        +--de.flexiprovider.api.Cipher
              |
              +--de.flexiprovider.api.AsymmetricBlockCipher
                    |
                    +--de.flexiprovider.core.elgamal.semanticallysecure.SSVElGamal

public class SSVElGamal

extends AsymmetricBlockCipher

This class implements a semantically secure variant of the original ElGamal encryption. The implementation is based on algorithm 14.2, page 476 of the book: Modern Cryptography - Theory & Practice by Wenbo Mao.

Author:

Thomas Wahrenbruch, Roberto Samarone dos Santos Araújo

Field Summary

static java.lang.String

ALG_NAME The algorithm name.

Fields inherited from class de.flexiprovider.api.AsymmetricBlockCipher

buf, cipherTextSize, maxPlainTextSize, paramSpec

Fields inherited from class de.flexiprovider.api.Cipher

DECRYPT_MODE, ENCRYPT_MODE, opMode

Constructor Summary

SSVElGamal()

Method Summary

int	getKeySize(Key key) Return the key size of the given key object in bits.
java.lang.String	getName() Return the name of this cipher.
protected void	initCipherDecrypt(Key key, AlgorithmParameterSpec params) Initialize the block cipher with a key for data encryption.
protected void	initCipherEncrypt(Key key, AlgorithmParameterSpec params, SecureRandom secureRandom) Initialize the block cipher with a key for data encryption.
protected byte[]	messageDecrypt(byte[] input) Decrypt a ciphertext.
protected byte[]	messageEncrypt(byte[] input) Encrypt a message.

Methods inherited from class de.flexiprovider.api.AsymmetricBlockCipher

checkLength, doFinal, doFinal, getBlockSize, getIV, getOutputSize, getParameters, initDecrypt, initDecrypt, initEncrypt, initEncrypt, initEncrypt, initEncrypt, setMode, setPadding, update, update

Methods inherited from class de.flexiprovider.api.Cipher

doFinal, doFinal, engineDoFinal, engineDoFinal, engineGetBlockSize, engineGetIV, engineGetKeySize, engineGetOutputSize, engineGetParameters, engineInit, engineInit, engineInit, engineSetMode, engineSetPadding, engineUpdate, engineUpdate, update

Methods inherited from class java.lang.Object

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

Field Detail

ALG_NAME

public static final java.lang.String ALG_NAME

The algorithm name.

Constructor Detail

SSVElGamal

public SSVElGamal()

Method Detail

getName

public java.lang.String getName()

Return the name of this cipher.

Overrides:

getName in class Cipher

Returns:

ALG_NAME

getKeySize

public int getKeySize(Key key)
               throws InvalidKeyException

Return the key size of the given key object in bits. Checks whether the key object is an instance of ElGamalPublicKey or ElGamalPrivateKey.

Overrides:

getKeySize in class Cipher

Parameters:

key - the key object

Returns:

the key size of the given key object.

Throws:

InvalidKeyException - if key is invalid.

initCipherEncrypt

protected void initCipherEncrypt(Key key,
                                 AlgorithmParameterSpec params,
                                 SecureRandom secureRandom)
                          throws InvalidKeyException

Initialize the block cipher with a key for data encryption. Parameters are currently not supported.

Overrides:

initCipherEncrypt in class AsymmetricBlockCipher

Parameters:

key - the key which has to be used to encrypt data.

params - the algorithm parameters.

secureRandom - a source of randomness.

Throws:

InvalidKeyException - if the given key is inappropriate for initializing this cipher.

initCipherDecrypt

protected void initCipherDecrypt(Key key,
                                 AlgorithmParameterSpec params)
                          throws InvalidKeyException

Initialize the block cipher with a key for data encryption. Parameters are currently not supported.

Overrides:

initCipherDecrypt in class AsymmetricBlockCipher

Parameters:

key - the key which has to be used to decrypt data.

params - the algorithm parameters.

Throws:

InvalidKeyException - if the given key is inappropriate for initializing this cipher.

messageEncrypt

protected byte[] messageEncrypt(byte[] input)

Encrypt a message.

Overrides:

messageEncrypt in class AsymmetricBlockCipher

Parameters:

input - the message

Returns:

the encrypted message

messageDecrypt

protected byte[] messageDecrypt(byte[] input)
                         throws BadPaddingException

Decrypt a ciphertext.

Overrides:

messageDecrypt in class AsymmetricBlockCipher

Parameters:

input - the ciphertext

Returns:

the decrypted ciphertext

Throws:

BadPaddingException - if the ciphertext is invalid.