package org.bouncycastle.crypto.engines;

import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.StreamCipher;
import org.bouncycastle.crypto.params.KeyParameter;

Implementation of Bob Jenkin's ISAAC (Indirection Shift Accumulate Add and Count). see: http://www.burtleburtle.net/bob/rand/isaacafa.html
/** * Implementation of Bob Jenkin's ISAAC (Indirection Shift Accumulate Add and Count). * see: http://www.burtleburtle.net/bob/rand/isaacafa.html */
public class ISAACEngine implements StreamCipher { // Constants private final int sizeL = 8, stateArraySize = sizeL<<5; // 256 // Cipher's internal state private int[] engineState = null, // mm results = null; // randrsl private int a = 0, b = 0, c = 0; // Engine state private int index = 0; private byte[] keyStream = new byte[stateArraySize<<2], // results expanded into bytes workingKey = null; private boolean initialised = false;
initialise an ISAAC cipher.
Params:
  • forEncryption – whether or not we are for encryption.
  • params – the parameters required to set up the cipher.
Throws:
/** * initialise an ISAAC cipher. * * @param forEncryption whether or not we are for encryption. * @param params the parameters required to set up the cipher. * @exception IllegalArgumentException if the params argument is * inappropriate. */
public void init( boolean forEncryption, CipherParameters params) { if (!(params instanceof KeyParameter)) { throw new IllegalArgumentException("invalid parameter passed to ISAAC init - " + params.getClass().getName()); } /* * ISAAC encryption and decryption is completely * symmetrical, so the 'forEncryption' is * irrelevant. */ KeyParameter p = (KeyParameter)params; setKey(p.getKey()); return; } public byte returnByte(byte in) { if (index == 0) { isaac(); keyStream = intToByteLittle(results); } byte out = (byte)(keyStream[index]^in); index = (index + 1) & 1023; return out; } public void processBytes( byte[] in, int inOff, int len, byte[] out, int outOff) { if (!initialised) { throw new IllegalStateException(getAlgorithmName()+" not initialised"); } if ((inOff + len) > in.length) { throw new DataLengthException("input buffer too short"); } if ((outOff + len) > out.length) { throw new DataLengthException("output buffer too short"); } for (int i = 0; i < len; i++) { if (index == 0) { isaac(); keyStream = intToByteLittle(results); } out[i+outOff] = (byte)(keyStream[index]^in[i+inOff]); index = (index + 1) & 1023; } } public String getAlgorithmName() { return "ISAAC"; } public void reset() { setKey(workingKey); } // Private implementation private void setKey(byte[] keyBytes) { workingKey = keyBytes; if (engineState == null) { engineState = new int[stateArraySize]; } if (results == null) { results = new int[stateArraySize]; } int i, j, k; // Reset state for (i = 0; i < stateArraySize; i++) { engineState[i] = results[i] = 0; } a = b = c = 0; // Reset index counter for output index = 0; // Convert the key bytes to ints and put them into results[] for initialization byte[] t = new byte[keyBytes.length + (keyBytes.length & 3)]; System.arraycopy(keyBytes, 0, t, 0, keyBytes.length); for (i = 0; i < t.length; i+=4) { results[i>>2] = byteToIntLittle(t, i); } // It has begun? int[] abcdefgh = new int[sizeL]; for (i = 0; i < sizeL; i++) { abcdefgh[i] = 0x9e3779b9; // Phi (golden ratio) } for (i = 0; i < 4; i++) { mix(abcdefgh); } for (i = 0; i < 2; i++) { for (j = 0; j < stateArraySize; j+=sizeL) { for (k = 0; k < sizeL; k++) { abcdefgh[k] += (i<1) ? results[j+k] : engineState[j+k]; } mix(abcdefgh); for (k = 0; k < sizeL; k++) { engineState[j+k] = abcdefgh[k]; } } } isaac(); initialised = true; } private void isaac() { int i, x, y; b += ++c; for (i = 0; i < stateArraySize; i++) { x = engineState[i]; switch (i & 3) { case 0: a ^= (a << 13); break; case 1: a ^= (a >>> 6); break; case 2: a ^= (a << 2); break; case 3: a ^= (a >>> 16); break; } a += engineState[(i+128) & 0xFF]; engineState[i] = y = engineState[(x >>> 2) & 0xFF] + a + b; results[i] = b = engineState[(y >>> 10) & 0xFF] + x; } } private void mix(int[] x) { x[0]^=x[1]<< 11; x[3]+=x[0]; x[1]+=x[2]; x[1]^=x[2]>>> 2; x[4]+=x[1]; x[2]+=x[3]; x[2]^=x[3]<< 8; x[5]+=x[2]; x[3]+=x[4]; x[3]^=x[4]>>>16; x[6]+=x[3]; x[4]+=x[5]; x[4]^=x[5]<< 10; x[7]+=x[4]; x[5]+=x[6]; x[5]^=x[6]>>> 4; x[0]+=x[5]; x[6]+=x[7]; x[6]^=x[7]<< 8; x[1]+=x[6]; x[7]+=x[0]; x[7]^=x[0]>>> 9; x[2]+=x[7]; x[0]+=x[1]; } private int byteToIntLittle(byte[] x, int offset) { return (int)(x[offset++] & 0xFF) | ((x[offset++] & 0xFF) << 8) | ((x[offset++] & 0xFF) << 16) | (x[offset++] << 24); } private byte[] intToByteLittle(int x) { byte[] out = new byte[4]; out[3] = (byte)x; out[2] = (byte)(x >>> 8); out[1] = (byte)(x >>> 16); out[0] = (byte)(x >>> 24); return out; } private byte[] intToByteLittle(int[] x) { byte[] out = new byte[4*x.length]; for (int i = 0, j = 0; i < x.length; i++,j+=4) { System.arraycopy(intToByteLittle(x[i]), 0, out, j, 4); } return out; } }