org.bouncycastle.crypto.modes
Class EAXBlockCipher

java.lang.Object
  org.bouncycastle.crypto.modes.EAXBlockCipher

All Implemented Interfaces:

AEADBlockCipher

public class EAXBlockCipher
extends java.lang.Object
implements AEADBlockCipher

A Two-Pass Authenticated-Encryption Scheme Optimized for Simplicity and Efficiency - by M. Bellare, P. Rogaway, D. Wagner. http://www.cs.ucdavis.edu/~rogaway/papers/eax.pdf EAX is an AEAD scheme based on CTR and OMAC1/CMAC, that uses a single block cipher to encrypt and authenticate data. It's on-line (the length of a message isn't needed to begin processing it), has good performances, it's simple and provably secure (provided the underlying block cipher is secure). Of course, this implementations is NOT thread-safe.

Field Summary

private byte[]	associatedTextMac
private int	blockSize
private byte[]	bufBlock
private int	bufOff
private SICBlockCipher	cipher
private static byte	cTAG
private boolean	forEncryption
private static byte	hTAG
private Mac	mac
private byte[]	macBlock
private int	macSize
private byte[]	nonceMac
private static byte	nTAG

Constructor Summary

EAXBlockCipher(BlockCipher cipher)
Constructor that accepts an instance of a block cipher engine.

Method Summary

private void	calculateMac()
int	doFinal(byte[] out, int outOff) Finish the operation either appending or verifying the MAC at the end of the data.
java.lang.String	getAlgorithmName() Return the name of the algorithm.
int	getBlockSize()
byte[]	getMac() Return the value of the MAC associated with the last stream processed.
int	getOutputSize(int len) return the size of the output buffer required for a processBytes plus a doFinal with an input of len bytes.
BlockCipher	getUnderlyingCipher() return the cipher this object wraps.
int	getUpdateOutputSize(int len) return the size of the output buffer required for a processBytes an input of len bytes.
void	init(boolean forEncryption, CipherParameters params) initialise the underlying cipher.
private int	process(byte b, byte[] out, int outOff)
int	processByte(byte in, byte[] out, int outOff) encrypt/decrypt a single byte.
int	processBytes(byte[] in, int inOff, int len, byte[] out, int outOff) process a block of bytes from in putting the result into out.
void	reset() Reset the cipher.
private boolean	verifyMac(byte[] mac, int off)

Methods inherited from class java.lang.Object

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

Field Detail

nTAG

private static final byte nTAG

See Also:

Constant Field Values

hTAG

private static final byte hTAG

See Also:

Constant Field Values

cTAG

private static final byte cTAG

See Also:

Constant Field Values

cipher

private SICBlockCipher cipher

forEncryption

private boolean forEncryption

blockSize

private int blockSize

mac

private Mac mac

nonceMac

private byte[] nonceMac

associatedTextMac

private byte[] associatedTextMac

macBlock

private byte[] macBlock

macSize

private int macSize

bufBlock

private byte[] bufBlock

bufOff

private int bufOff

Constructor Detail

EAXBlockCipher

public EAXBlockCipher(BlockCipher cipher)

Constructor that accepts an instance of a block cipher engine.

Parameters:

cipher - the engine to use

Method Detail

getAlgorithmName

public java.lang.String getAlgorithmName()

Description copied from interface: AEADBlockCipher

Return the name of the algorithm.

Specified by:

getAlgorithmName in interface AEADBlockCipher

Returns:

the algorithm name.

getUnderlyingCipher

public BlockCipher getUnderlyingCipher()

Description copied from interface: AEADBlockCipher

return the cipher this object wraps.

Specified by:

getUnderlyingCipher in interface AEADBlockCipher

Returns:

the cipher this object wraps.

getBlockSize

public int getBlockSize()

init

public void init(boolean forEncryption,
                 CipherParameters params)
          throws java.lang.IllegalArgumentException

Description copied from interface: AEADBlockCipher

initialise the underlying cipher. Parameter can either be an AEADParameters or a ParametersWithIV object.

Specified by:

init in interface AEADBlockCipher

Parameters:

forEncryption - true if we are setting up for encryption, false otherwise.

params - the necessary parameters for the underlying cipher to be initialised.

Throws:

java.lang.IllegalArgumentException - if the params argument is inappropriate.

calculateMac

private void calculateMac()

reset

public void reset()

Description copied from interface: AEADBlockCipher

Reset the cipher. After resetting the cipher is in the same state as it was after the last init (if there was one).

Specified by:

reset in interface AEADBlockCipher

processByte

public int processByte(byte in,
                       byte[] out,
                       int outOff)
                throws DataLengthException

Description copied from interface: AEADBlockCipher

encrypt/decrypt a single byte.

Specified by:

processByte in interface AEADBlockCipher

Parameters:

in - the byte to be processed.

out - the output buffer the processed byte goes into.

outOff - the offset into the output byte array the processed data starts at.

Returns:

the number of bytes written to out.

Throws:

DataLengthException - if the output buffer is too small.

processBytes

public int processBytes(byte[] in,
                        int inOff,
                        int len,
                        byte[] out,
                        int outOff)
                 throws DataLengthException

Description copied from interface: AEADBlockCipher

process a block of bytes from in putting the result into out.

Specified by:

processBytes in interface AEADBlockCipher

Parameters:

in - the input byte array.

inOff - the offset into the in array where the data to be processed starts.

len - the number of bytes to be processed.

out - the output buffer the processed bytes go into.

outOff - the offset into the output byte array the processed data starts at.

Returns:

the number of bytes written to out.

Throws:

DataLengthException - if the output buffer is too small.

doFinal

public int doFinal(byte[] out,
                   int outOff)
            throws java.lang.IllegalStateException,
                   InvalidCipherTextException

Description copied from interface: AEADBlockCipher

Finish the operation either appending or verifying the MAC at the end of the data.

Specified by:

doFinal in interface AEADBlockCipher

Parameters:

out - space for any resulting output data.

outOff - offset into out to start copying the data at.

Returns:

number of bytes written into out.

Throws:

java.lang.IllegalStateException - if the cipher is in an inappropriate state.

InvalidCipherTextException - if the MAC fails to match.

getMac

public byte[] getMac()

Description copied from interface: AEADBlockCipher

Return the value of the MAC associated with the last stream processed.

Specified by:

getMac in interface AEADBlockCipher

Returns:

MAC for plaintext data.

getUpdateOutputSize

public int getUpdateOutputSize(int len)

Description copied from interface: AEADBlockCipher

return the size of the output buffer required for a processBytes an input of len bytes.

Specified by:

getUpdateOutputSize in interface AEADBlockCipher

Parameters:

len - the length of the input.

Returns:

the space required to accommodate a call to processBytes with len bytes of input.

getOutputSize

public int getOutputSize(int len)

Description copied from interface: AEADBlockCipher

return the size of the output buffer required for a processBytes plus a doFinal with an input of len bytes.

Specified by:

getOutputSize in interface AEADBlockCipher

Parameters:

len - the length of the input.

Returns:

the space required to accommodate a call to processBytes and doFinal with len bytes of input.

process

private int process(byte b,
                    byte[] out,
                    int outOff)

verifyMac

private boolean verifyMac(byte[] mac,
                          int off)