org.spongycastle.crypto.engines

Class CramerShoupCoreEngine

java.lang.Object

org.spongycastle.crypto.engines.CramerShoupCoreEngine

public class CramerShoupCoreEngine
extends java.lang.Object

Essentially the Cramer-Shoup encryption / decryption algorithms according to "A practical public key cryptosystem provably secure against adaptive chosen ciphertext attack." (Crypto 1998)

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CramerShoupCoreEngine.CramerShoupCiphertextException CS exception for wrong cipher-texts

Constructor Summary

Constructors

Constructor and Description
CramerShoupCoreEngine()

Method Summary

Modifier and Type	Method and Description
java.math.BigInteger	convertInput(byte[] in, int inOff, int inLen)
byte[]	convertOutput(java.math.BigInteger result)
java.math.BigInteger	decryptBlock(CramerShoupCiphertext input)
CramerShoupCiphertext	encryptBlock(java.math.BigInteger input)
int	getInputBlockSize() Return the maximum size for an input block to this engine.
int	getOutputBlockSize() Return the maximum size for an output block to this engine.
void	init(boolean forEncryption, CipherParameters param) initialise the CramerShoup engine.
void	init(boolean forEncryption, CipherParameters param, java.lang.String label) initialise the CramerShoup engine.
protected java.security.SecureRandom	initSecureRandom(boolean needed, java.security.SecureRandom provided)

Methods inherited from class java.lang.Object

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

Constructor Detail

CramerShoupCoreEngine

public CramerShoupCoreEngine()

Method Detail

init

public void init(boolean forEncryption,
                 CipherParameters param,
                 java.lang.String label)

initialise the CramerShoup engine.

Parameters:

forEncryption - whether this engine should encrypt or decrypt

param - the necessary CramerShoup key parameters.

label - the label for labelled CS as String

init

public void init(boolean forEncryption,
                 CipherParameters param)

initialise the CramerShoup engine.

Parameters:

forEncryption - whether this engine should encrypt or decrypt

param - the necessary CramerShoup key parameters.

getInputBlockSize

public int getInputBlockSize()

Return the maximum size for an input block to this engine. For Cramer Shoup this is always one byte less than the key size on encryption, and the same length as the key size on decryption. TODO: correct?

Returns:

maximum size for an input block.

getOutputBlockSize

public int getOutputBlockSize()

Return the maximum size for an output block to this engine. For Cramer Shoup this is always one byte less than the key size on decryption, and the same length as the key size on encryption. TODO: correct?

Returns:

maximum size for an output block.

convertInput

public java.math.BigInteger convertInput(byte[] in,
                                         int inOff,
                                         int inLen)

convertOutput

public byte[] convertOutput(java.math.BigInteger result)

encryptBlock

public CramerShoupCiphertext encryptBlock(java.math.BigInteger input)

decryptBlock

public java.math.BigInteger decryptBlock(CramerShoupCiphertext input)
                                  throws CramerShoupCoreEngine.CramerShoupCiphertextException

Throws:

CramerShoupCoreEngine.CramerShoupCiphertextException

initSecureRandom

protected java.security.SecureRandom initSecureRandom(boolean needed,
                                                      java.security.SecureRandom provided)