org.bouncycastle.crypto.modes

Class OldCTSBlockCipher

java.lang.Object

org.bouncycastle.crypto.DefaultBufferedBlockCipher

org.bouncycastle.crypto.modes.OldCTSBlockCipher

All Implemented Interfaces:

BufferedBlockCipher

public class OldCTSBlockCipher
extends DefaultBufferedBlockCipher

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.

This version applies the CTS algorithm from one block up, rather than following the errata update issued in 2004, where CTS mode is applied from greater than 1 block up and the first block is processed using CBC mode.

Field Summary

Fields inherited from class org.bouncycastle.crypto.DefaultBufferedBlockCipher

buf, bufOff, cipher, forEncryption, partialBlockOkay, pgpCFB

Constructor Summary

Constructors

Constructor and Description
OldCTSBlockCipher(BlockCipher cipher) Create a buffered block cipher that uses Cipher Text Stealing

Method Summary

Modifier and Type	Method and Description
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 necessary.
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.bouncycastle.crypto.DefaultBufferedBlockCipher

getBlockSize, getUnderlyingCipher, init, reset, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

OldCTSBlockCipher

public OldCTSBlockCipher(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.

Specified by:

getUpdateOutputSize in interface BufferedBlockCipher

Overrides:

getUpdateOutputSize in class DefaultBufferedBlockCipher

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.

Specified by:

getOutputSize in interface BufferedBlockCipher

Overrides:

getOutputSize in class DefaultBufferedBlockCipher

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,
                       java.lang.IllegalStateException

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

Specified by:

processByte in interface BufferedBlockCipher

Overrides:

processByte in class DefaultBufferedBlockCipher

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.

java.lang.IllegalStateException - if the cipher isn't initialised.

processBytes

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

process an array of bytes, producing output if necessary.

Specified by:

processBytes in interface BufferedBlockCipher

Overrides:

processBytes in class DefaultBufferedBlockCipher

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.

java.lang.IllegalStateException - if the cipher isn't initialised.

doFinal

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

Process the last block in the buffer.

Specified by:

doFinal in interface BufferedBlockCipher

Overrides:

doFinal in class DefaultBufferedBlockCipher

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.

java.lang.IllegalStateException - if the underlying cipher is not initialised.

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