org.gudy.bouncycastle.crypto.modes
Class CTSBlockCipher

java.lang.Object
  org.gudy.bouncycastle.crypto.BufferedBlockCipher
      org.gudy.bouncycastle.crypto.modes.CTSBlockCipher

public class CTSBlockCipher
extends BufferedBlockCipher

A Cipher Text Stealing (CTS) mode cipher. CTS allows block ciphers to be used to produce cipher text which is the same length as the plain text.

Field Summary

Fields inherited from class org.gudy.bouncycastle.crypto.BufferedBlockCipher

buf, bufOff, cipher, forEncryption, partialBlockOkay, pgpCFB

Constructor Summary

CTSBlockCipher(BlockCipher cipher)
Create a buffered block cipher that uses Cipher Text Stealing

Method Summary

int	doFinal(byte[] out, int outOff) Process the last block in the buffer.
int	getOutputSize(int len) return the size of the output buffer required for an update plus a doFinal with an input of len bytes.
int	getUpdateOutputSize(int len) return the size of the output buffer required for an update an input of len bytes.
int	processByte(byte in, byte[] out, int outOff) process a single byte, producing an output block if neccessary.
int	processBytes(byte[] in, int inOff, int len, byte[] out, int outOff) process an array of bytes, producing output if necessary.

Methods inherited from class org.gudy.bouncycastle.crypto.BufferedBlockCipher

getBlockSize, getUnderlyingCipher, init, reset

Methods inherited from class java.lang.Object

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

Constructor Detail

CTSBlockCipher

public CTSBlockCipher(BlockCipher cipher)

Create a buffered block cipher that uses Cipher Text Stealing

Parameters:

cipher - the underlying block cipher this buffering object wraps.

Method Detail

getUpdateOutputSize

public int getUpdateOutputSize(int len)

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

Overrides:

getUpdateOutputSize in class BufferedBlockCipher

Parameters:

len - the length of the input.

Returns:

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

getOutputSize

public int getOutputSize(int len)

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

Overrides:

getOutputSize in class BufferedBlockCipher

Parameters:

len - the length of the input.

Returns:

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

processByte

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

process a single byte, producing an output block if neccessary.

Overrides:

processByte in class BufferedBlockCipher

Parameters:

in - the input byte.

out - the space for any output that might be produced.

outOff - the offset from which the output will be copied.

Returns:

the number of output bytes copied to out.

Throws:

DataLengthException - if there isn't enough space in out.

IllegalStateException - if the cipher isn't initialised.

processBytes

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

process an array of bytes, producing output if necessary.

Overrides:

processBytes in class BufferedBlockCipher

Parameters:

in - the input byte array.

inOff - the offset at which the input data starts.

len - the number of bytes to be copied out of the input array.

out - the space for any output that might be produced.

outOff - the offset from which the output will be copied.

Returns:

the number of output bytes copied to out.

Throws:

DataLengthException - if there isn't enough space in out.

IllegalStateException - if the cipher isn't initialised.

doFinal

public int doFinal(byte[] out,
                   int outOff)
            throws DataLengthException,
                   IllegalStateException,
                   InvalidCipherTextException

Process the last block in the buffer.

Overrides:

doFinal in class BufferedBlockCipher

Parameters:

out - the array the block currently being held is copied into.

outOff - the offset at which the copying starts.

Returns:

the number of output bytes copied to out.

Throws:

DataLengthException - if there is insufficient space in out for the output.

IllegalStateException - if the underlying cipher is not initialised.

InvalidCipherTextException - if cipher text decrypts wrongly (in case the exception will never get thrown).