org.spongycastle.crypto.modes

Class NISTCTSBlockCipher

java.lang.Object

org.spongycastle.crypto.BufferedBlockCipher

org.spongycastle.crypto.modes.NISTCTSBlockCipher

public class NISTCTSBlockCipher
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.

This class implements the NIST version as documented in "Addendum to NIST SP 800-38A, Recommendation for Block Cipher Modes of Operation: Three Variants of Ciphertext Stealing for CBC Mode"

Field Summary

Fields

Modifier and Type	Field and Description
static int	CS1
static int	CS2
static int	CS3

Fields inherited from class org.spongycastle.crypto.BufferedBlockCipher

buf, bufOff, cipher, forEncryption, partialBlockOkay, pgpCFB

Constructor Summary

Constructors

Constructor and Description
NISTCTSBlockCipher(int type, BlockCipher cipher) Create a buffered block cipher that uses NIST 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.spongycastle.crypto.BufferedBlockCipher

getBlockSize, getUnderlyingCipher, init, reset

Methods inherited from class java.lang.Object

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

Field Detail

CS1

public static final int CS1

See Also:

Constant Field Values

CS2

public static final int CS2

See Also:

Constant Field Values

CS3

public static final int CS3

See Also:

Constant Field Values

Constructor Detail

NISTCTSBlockCipher

public NISTCTSBlockCipher(int type,
                          BlockCipher cipher)

Create a buffered block cipher that uses NIST Cipher Text Stealing

Parameters:

type - type of CTS mode (CS1, CS2, or CS3)

cipher - the underlying block cipher used to create the CBC block cipher this cipher uses..

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,
                       java.lang.IllegalStateException

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

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.

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.

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.

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.

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.

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

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