iaik.security.elgamal

Class ElGamal

java.lang.Object

javax.crypto.CipherSpi

iaik.security.elgamal.ElGamal

public class ElGamal
extends javax.crypto.CipherSpi

This class implements the ElGamal Cipher algorithm of fields of prime characteristic. It allows to encrypt a single block and offers support for PKCS1 padding.

Constructor Summary

Constructors

Constructor and Description
ElGamal() Default Constructor for the ELGamal cipher.

Method Summary

Methods

Modifier and Type	Method and Description
protected byte[]	engineDoFinal(byte[] input, int inputOffset, int inputLen) En/decrypts the given data.
protected int	engineDoFinal(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset) En/decrypts the given data.
protected int	engineGetBlockSize()
protected byte[]	engineGetIV() This method return null, because this cipher does not use an IV.
protected int	engineGetOutputSize(int inputLen)
protected java.security.AlgorithmParameters	engineGetParameters() Returns the algorithm parameters
protected void	engineInit(int opmode, java.security.Key key, java.security.spec.AlgorithmParameterSpec params, java.security.SecureRandom random) Initializes this ElGamal cipher with given key and algorithm parameters.
protected void	engineInit(int opmode, java.security.Key key, java.security.AlgorithmParameters params, java.security.SecureRandom random) Initializes this ElGamal cipher with given key and parameters (if specified).
protected void	engineInit(int opmode, java.security.Key key, java.security.SecureRandom random) Initializes this ElGamal cipher with the given key.
protected void	engineSetMode(java.lang.String mode) Sets the transformation mode.
protected void	engineSetPadding(java.lang.String padding) Sets the padding scheme of this cipher, which only can be "PKCS1Padding" or "NoPadding".
protected byte[]	engineUpdate(byte[] in, int inOff, int inLen) Updates this Cipher with the given bytes.
protected int	engineUpdate(byte[] in, int inOff, int inLen, byte[] out, int outOff) Updates this Cipher with the given bytes.

Methods inherited from class javax.crypto.CipherSpi

engineDoFinal, engineGetKeySize, engineUnwrap, engineUpdate, engineUpdateAAD, engineUpdateAAD, engineWrap

Methods inherited from class java.lang.Object

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

Constructor Detail

ElGamal

public ElGamal()

Default Constructor for the ELGamal cipher. Sets the Padding scheme to "PKCS1Padding" and mode to "ECB".

This constructor only internally is used for initializing an ElGamal Cipher. Applications should not call this constructor to get an ElGamal Cipher; they should call one of the Cipher.getInstance factory methods instead, e.g.:

 Cipher elGamal = Cipher.getInstance("ElGamal/ECB/PKCSPadding");
 

See Also:

Cipher.getInstance(java.lang.String)

Method Detail

engineUpdate

protected byte[] engineUpdate(byte[] in,
                  int inOff,
                  int inLen)

Updates this Cipher with the given bytes. This method only buffers the given bytes to be used for the final en/decrypting operation when method doFinal/ is called.

Specified by:

engineUpdate in class javax.crypto.CipherSpi

Parameters:

in - the input data as byte array

inOff - the start position in the input array

inLen - the number of bytes that should be processed, starting at inOff

Returns:

always null since no output is produced by this method

See Also:

CipherSpi.engineUpdate(byte[], int, int)

engineUpdate

protected int engineUpdate(byte[] in,
               int inOff,
               int inLen,
               byte[] out,
               int outOff)

Updates this Cipher with the given bytes. This method only buffers the given bytes to be used for the final en/decrypting operation when method doFinal/ is called.

Specified by:

engineUpdate in class javax.crypto.CipherSpi

Parameters:

in - the input data as byte array

inOff - the start position in the input array

inLen - the number of bytes that should be processed, starting at inOff

out - the byte array to which to write the result; ignored

outOff - the start position in the output array; ignored

Returns:

always 0 since no output is produced by this method

Throws:

javax.crypto.ShortBufferException - never thrown

See Also:

CipherSpi.engineUpdate(byte[], int, int, byte[], int)

engineGetBlockSize

protected int engineGetBlockSize()

Specified by:

engineGetBlockSize in class javax.crypto.CipherSpi

engineGetIV

protected byte[] engineGetIV()

This method return null, because this cipher does not use an IV.

Specified by:

engineGetIV in class javax.crypto.CipherSpi

Returns:

null.

engineGetOutputSize

protected int engineGetOutputSize(int inputLen)

Specified by:

engineGetOutputSize in class javax.crypto.CipherSpi

engineGetParameters

protected java.security.AlgorithmParameters engineGetParameters()

Returns the algorithm parameters

Specified by:

engineGetParameters in class javax.crypto.CipherSpi

Returns:

the algorithm parameters

engineInit

protected void engineInit(int opmode,
              java.security.Key key,
              java.security.SecureRandom random)
                   throws java.security.InvalidKeyException

Initializes this ElGamal cipher with the given key.

Before a cipher object is ready for data processing, it has to be initialized according to the desired cryptographic operation, which is specified by the opmode parameter (either ENCRYPT_MODE or DECRYPT_MODE, or WRAP_MODE or UNWRAP_MODE).

The key either will be a ElGamalPrivateKey or a ElGamalPublicKey, depending on the specific cryptographic operation to be performed.

Applications shall use the corresponding init method of javax.crypto.Cipher for provider independently initializing an ElGamal cipher.

Specified by:

engineInit in class javax.crypto.CipherSpi

Parameters:

opmode - Cipher.ENCRYPT_MODE or Cipher.DECRYPT_MODE or Cipher.WRAP_MODE or Cipher.UNWRAP_MODE

key - an instance of an ElGamal PublicKey or ElGamal PrivateKey

random - source of randomness

Throws:

java.security.InvalidKeyException - if the key is invalid (not a valid ElGamal key), or if PKCS1Padding is used and the key is not appropriate for the block type, or if a private key is tried to be used for an encryption operation or a public key is tried to be for a decryption operation

engineInit

protected void engineInit(int opmode,
              java.security.Key key,
              java.security.spec.AlgorithmParameterSpec params,
              java.security.SecureRandom random)
                   throws java.security.InvalidKeyException,
                          java.security.InvalidAlgorithmParameterException

Initializes this ElGamal cipher with given key and algorithm parameters.

Before a cipher object is ready for data processing, it has to be initialized according to the desired cryptographic operation, which is specified by the opmode parameter (either ENCRYPT_MODE or DECRYPT_MODE, or WRAP_MODE or UNWRAP_MODE).

The key either will be a ElGamalPrivateKey or a ElGamalPublicKey, depending on the specific cryptographic operation to be performed.

Applications shall use the corresponding init method of javax.crypto.Cipher for provider independently initializing an ElGamal cipher.

Specified by:

engineInit in class javax.crypto.CipherSpi

Parameters:

opmode - Cipher.ENCRYPT_MODE or Cipher.DECRYPT_MODE or Cipher.WRAP_MODE or Cipher.UNWRAP_MODE

key - an instance of an ElGamal PublicKey or ElGamal PrivateKey

params - algorithm parameters

random - source of randomness

Throws:

java.security.InvalidAlgorithmParameterException - if the parameters are invalid

java.security.InvalidKeyException - if the key is invalid (not a valid ElGamal key), or if PKCS1Padding is used and the key is not appropriate for the block type, or if private key is tried to be used for an encryption operation or a public key is tried to be for a decryption operation

engineInit

protected void engineInit(int opmode,
              java.security.Key key,
              java.security.AlgorithmParameters params,
              java.security.SecureRandom random)
                   throws java.security.InvalidKeyException,
                          java.security.InvalidAlgorithmParameterException

Initializes this ElGamal cipher with given key and parameters (if specified).

Before a cipher object is ready for data processing, it has to be initialized according to the desired cryptographic operation, which is specified by the opmode parameter (either ENCRYPT_MODE or DECRYPT_MODE, or WRAP_MODE or UNWRAP_MODE).

The key either will be a ElGamalPrivateKey or a ElGamalPublicKey, depending on the specific cryptographic operation to be performed.

Applications shall use the corresponding init method of javax.crypto.Cipher for provider independently initializing an ElGamal cipher.

Specified by:

engineInit in class javax.crypto.CipherSpi

Parameters:

opmode - Cipher.ENCRYPT_MODE or Cipher.DECRYPT_MODE or Cipher.WRAP_MODE or Cipher.UNWRAP_MODE

key - an instance of a ElGamal PublicKey or ElGamal PrivateKey

params - algorithm parameters that may be used for OAEP padding

random - source of randomness

Throws:

java.security.InvalidAlgorithmParameterException - if the parameters are invalid

java.security.InvalidKeyException - if the key is invalid (not a valid ElGamal key), or if PKCS1Padding is used and the key is not appropriate for the block type, or if private key is tried to be used for an encryption operation or a public key is tried to be for a decryption operation

engineSetMode

protected void engineSetMode(java.lang.String mode)
                      throws java.security.NoSuchAlgorithmException

Sets the transformation mode.

For PKCS#1v1.5 padding this might be "ECB" (automatic block type selection) or the padding block type ("0" or "1" for a private key operation, and "2" for a public key operation.

Specified by:

engineSetMode in class javax.crypto.CipherSpi

Parameters:

mode - the transformation mode ("ECB" or PKCS#1v1.5 block type ("0","1" or "2")

Throws:

java.security.NoSuchAlgorithmException

engineSetPadding

protected void engineSetPadding(java.lang.String padding)
                         throws javax.crypto.NoSuchPaddingException

Sets the padding scheme of this cipher, which only can be "PKCS1Padding" or "NoPadding".

Specified by:

engineSetPadding in class javax.crypto.CipherSpi

Parameters:

padding - the padding scheme for this ElGamal cipher

Throws:

javax.crypto.NoSuchPaddingException - if the requested padding algorithm is not supported, or cannot be supported (because, for instance, required parameters are not available)

engineDoFinal

protected byte[] engineDoFinal(byte[] input,
                   int inputOffset,
                   int inputLen)
                        throws javax.crypto.IllegalBlockSizeException,
                               javax.crypto.BadPaddingException

En/decrypts the given data.

Applications shall use the corresponding doFinal method of javax.crypto.Cipher for provider independently doing the data en/decryption.

The data to be processed is given in an input byte array. Beginning at inputOffset, only the first inputLen bytes are en/decrypted. The result is returned as an output byte array.

Specified by:

engineDoFinal in class javax.crypto.CipherSpi

Parameters:

input - the byte array holding the data to be processed

inputOffset - the offset indicating the start position within the input byte array

inputLen - the number of bytes to be processed

Returns:

the byte array containing the en/decrypted data

Throws:

javax.crypto.BadPaddingException - if a padding problem occurs

javax.crypto.IllegalBlockSizeException

See Also:

Cipher.doFinal(), CipherSpi.engineDoFinal(byte[], int, int)

engineDoFinal

protected int engineDoFinal(byte[] input,
                int inputOffset,
                int inputLen,
                byte[] output,
                int outputOffset)
                     throws javax.crypto.ShortBufferException,
                            javax.crypto.IllegalBlockSizeException,
                            javax.crypto.BadPaddingException

En/decrypts the given data.

Applications shall use the corresponding doFinal method of javax.crypto.Cipher for provider independent doing the data en/decryption.

The data to be processed is given in an input byte array. Beginning at inputOffset, only the first inputLen bytes are en/decrypted. The result is stored in the given output byte array, beginning at outputOffset. The number of bytes stored in this byte array are returned.

Specified by:

engineDoFinal in class javax.crypto.CipherSpi

Parameters:

input - the byte array holding the data to be processed

inputOffset - the offset indicating the start position within the input byte array

inputLen - the number of bytes to be processed

output - the byte array for holding the result

outputOffset - the offset indicating the start position within the output byte array to which the en/decrypted data is written

Returns:

the number of bytes stored in the output byte array

Throws:

javax.crypto.ShortBufferException - if the given output buffer is too small for holding the result

javax.crypto.BadPaddingException - if a padding problem occurs

javax.crypto.IllegalBlockSizeException

See Also:

Cipher.doFinal(), CipherSpi.engineDoFinal(byte[], int, int)