org.bouncycastle.crypto.engines

Class Salsa20Engine

java.lang.Object

org.bouncycastle.crypto.engines.Salsa20Engine

All Implemented Interfaces:

SkippingCipher, SkippingStreamCipher, StreamCipher

Direct Known Subclasses:

ChaCha7539Engine, ChaChaEngine, XSalsa20Engine

public class Salsa20Engine
extends java.lang.Object
implements SkippingStreamCipher

Implementation of Daniel J. Bernstein's Salsa20 stream cipher, Snuffle 2005

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_ROUNDS
protected int[]	engineState
protected int	rounds
protected static byte[]	sigma Deprecated.
protected static byte[]	tau Deprecated.
protected int[]	x

Constructor Summary

Constructors

Constructor and Description
Salsa20Engine() Creates a 20 round Salsa20 engine.
Salsa20Engine(int rounds) Creates a Salsa20 engine with a specific number of rounds.

Method Summary

Modifier and Type	Method and Description
protected void	advanceCounter()
protected void	advanceCounter(long diff)
protected void	generateKeyStream(byte[] output)
java.lang.String	getAlgorithmName() Return the name of the algorithm the cipher implements.
protected long	getCounter()
protected int	getNonceSize()
long	getPosition() Return the current "position" of the cipher
void	init(boolean forEncryption, CipherParameters params) initialise a Salsa20 cipher.
protected void	packTauOrSigma(int keyLength, int[] state, int stateOffset)
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.
protected void	resetCounter()
protected void	retreatCounter()
protected void	retreatCounter(long diff)
byte	returnByte(byte in) encrypt/decrypt a single byte returning the result.
protected static int	rotl(int x, int y) Rotate left
static void	salsaCore(int rounds, int[] input, int[] x) Salsa20 function
long	seekTo(long position) Reset the cipher and then skip forward to a given position.
protected void	setKey(byte[] keyBytes, byte[] ivBytes)
long	skip(long numberOfBytes) Skip numberOfBytes forwards, or backwards.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_ROUNDS

public static final int DEFAULT_ROUNDS

See Also:

Constant Field Values

sigma

protected static final byte[] sigma

Deprecated.

tau

protected static final byte[] tau

Deprecated.

rounds

protected int rounds

engineState

protected int[] engineState

x

protected int[] x

Constructor Detail

Salsa20Engine

public Salsa20Engine()

Creates a 20 round Salsa20 engine.

Salsa20Engine

public Salsa20Engine(int rounds)

Creates a Salsa20 engine with a specific number of rounds.

Parameters:

rounds - the number of rounds (must be an even number).

Method Detail

packTauOrSigma

protected void packTauOrSigma(int keyLength,
                              int[] state,
                              int stateOffset)

init

public void init(boolean forEncryption,
                 CipherParameters params)

initialise a Salsa20 cipher.

Specified by:

init in interface StreamCipher

Parameters:

forEncryption - whether or not we are for encryption.

params - the parameters required to set up the cipher.

Throws:

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

getNonceSize

protected int getNonceSize()

getAlgorithmName

public java.lang.String getAlgorithmName()

Description copied from interface: StreamCipher

Return the name of the algorithm the cipher implements.

Specified by:

getAlgorithmName in interface StreamCipher

Returns:

the name of the algorithm the cipher implements.

returnByte

public byte returnByte(byte in)

Description copied from interface: StreamCipher

encrypt/decrypt a single byte returning the result.

Specified by:

returnByte in interface StreamCipher

Parameters:

in - the byte to be processed.

Returns:

the result of processing the input byte.

advanceCounter

protected void advanceCounter(long diff)

advanceCounter

protected void advanceCounter()

retreatCounter

protected void retreatCounter(long diff)

retreatCounter

protected void retreatCounter()

processBytes

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

Description copied from interface: StreamCipher

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

Specified by:

processBytes in interface StreamCipher

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 produced - should always be len.

skip

public long skip(long numberOfBytes)

Description copied from interface: SkippingCipher

Skip numberOfBytes forwards, or backwards.

Specified by:

skip in interface SkippingCipher

Parameters:

numberOfBytes - the number of bytes to skip (positive forward, negative backwards).

Returns:

the number of bytes actually skipped.

seekTo

public long seekTo(long position)

Description copied from interface: SkippingCipher

Reset the cipher and then skip forward to a given position.

Specified by:

seekTo in interface SkippingCipher

Parameters:

position - the number of bytes in to set the cipher state to.

Returns:

the byte position moved to.

getPosition

public long getPosition()

Description copied from interface: SkippingCipher

Return the current "position" of the cipher

Specified by:

getPosition in interface SkippingCipher

Returns:

the current byte position.

reset

public void reset()

Description copied from interface: StreamCipher

reset the cipher. This leaves it in the same state it was at after the last init (if there was one).

Specified by:

reset in interface StreamCipher

getCounter

protected long getCounter()

resetCounter

protected void resetCounter()

setKey

protected void setKey(byte[] keyBytes,
                      byte[] ivBytes)

generateKeyStream

protected void generateKeyStream(byte[] output)

salsaCore

public static void salsaCore(int rounds,
                             int[] input,
                             int[] x)

Salsa20 function

Parameters:

input - input data

rotl

protected static int rotl(int x,
                          int y)

Rotate left

Parameters:

x - value to rotate

y - amount to rotate x

Returns:

rotated x