GordianSnow3GEngine.java
/*
* GordianKnot: Security Suite
* Copyright 2012-2026. Tony Washer
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy
* of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package io.github.tonywasher.joceanus.gordianknot.impl.ext.engines;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.OutputLengthException;
import org.bouncycastle.crypto.StreamCipher;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;
import org.bouncycastle.util.Memoable;
/**
* Snow3GEngine implementation.
* Based on https://www.gsma.com/aboutus/wp-content/uploads/2014/12/snow3gspec.pdf
*/
@SuppressWarnings("checkstyle:MagicNumber")
public class GordianSnow3GEngine
implements StreamCipher, Memoable {
/**
* Rijndael S-box SR.
*/
private static final byte[] SR = {
(byte) 0x63, (byte) 0x7C, (byte) 0x77, (byte) 0x7B, (byte) 0xF2, (byte) 0x6B, (byte) 0x6F, (byte) 0xC5,
(byte) 0x30, (byte) 0x01, (byte) 0x67, (byte) 0x2B, (byte) 0xFE, (byte) 0xD7, (byte) 0xAB, (byte) 0x76,
(byte) 0xCA, (byte) 0x82, (byte) 0xC9, (byte) 0x7D, (byte) 0xFA, (byte) 0x59, (byte) 0x47, (byte) 0xF0,
(byte) 0xAD, (byte) 0xD4, (byte) 0xA2, (byte) 0xAF, (byte) 0x9C, (byte) 0xA4, (byte) 0x72, (byte) 0xC0,
(byte) 0xB7, (byte) 0xFD, (byte) 0x93, (byte) 0x26, (byte) 0x36, (byte) 0x3F, (byte) 0xF7, (byte) 0xCC,
(byte) 0x34, (byte) 0xA5, (byte) 0xE5, (byte) 0xF1, (byte) 0x71, (byte) 0xD8, (byte) 0x31, (byte) 0x15,
(byte) 0x04, (byte) 0xC7, (byte) 0x23, (byte) 0xC3, (byte) 0x18, (byte) 0x96, (byte) 0x05, (byte) 0x9A,
(byte) 0x07, (byte) 0x12, (byte) 0x80, (byte) 0xE2, (byte) 0xEB, (byte) 0x27, (byte) 0xB2, (byte) 0x75,
(byte) 0x09, (byte) 0x83, (byte) 0x2C, (byte) 0x1A, (byte) 0x1B, (byte) 0x6E, (byte) 0x5A, (byte) 0xA0,
(byte) 0x52, (byte) 0x3B, (byte) 0xD6, (byte) 0xB3, (byte) 0x29, (byte) 0xE3, (byte) 0x2F, (byte) 0x84,
(byte) 0x53, (byte) 0xD1, (byte) 0x00, (byte) 0xED, (byte) 0x20, (byte) 0xFC, (byte) 0xB1, (byte) 0x5B,
(byte) 0x6A, (byte) 0xCB, (byte) 0xBE, (byte) 0x39, (byte) 0x4A, (byte) 0x4C, (byte) 0x58, (byte) 0xCF,
(byte) 0xD0, (byte) 0xEF, (byte) 0xAA, (byte) 0xFB, (byte) 0x43, (byte) 0x4D, (byte) 0x33, (byte) 0x85,
(byte) 0x45, (byte) 0xF9, (byte) 0x02, (byte) 0x7F, (byte) 0x50, (byte) 0x3C, (byte) 0x9F, (byte) 0xA8,
(byte) 0x51, (byte) 0xA3, (byte) 0x40, (byte) 0x8F, (byte) 0x92, (byte) 0x9D, (byte) 0x38, (byte) 0xF5,
(byte) 0xBC, (byte) 0xB6, (byte) 0xDA, (byte) 0x21, (byte) 0x10, (byte) 0xFF, (byte) 0xF3, (byte) 0xD2,
(byte) 0xCD, (byte) 0x0C, (byte) 0x13, (byte) 0xEC, (byte) 0x5F, (byte) 0x97, (byte) 0x44, (byte) 0x17,
(byte) 0xC4, (byte) 0xA7, (byte) 0x7E, (byte) 0x3D, (byte) 0x64, (byte) 0x5D, (byte) 0x19, (byte) 0x73,
(byte) 0x60, (byte) 0x81, (byte) 0x4F, (byte) 0xDC, (byte) 0x22, (byte) 0x2A, (byte) 0x90, (byte) 0x88,
(byte) 0x46, (byte) 0xEE, (byte) 0xB8, (byte) 0x14, (byte) 0xDE, (byte) 0x5E, (byte) 0x0B, (byte) 0xDB,
(byte) 0xE0, (byte) 0x32, (byte) 0x3A, (byte) 0x0A, (byte) 0x49, (byte) 0x06, (byte) 0x24, (byte) 0x5C,
(byte) 0xC2, (byte) 0xD3, (byte) 0xAC, (byte) 0x62, (byte) 0x91, (byte) 0x95, (byte) 0xE4, (byte) 0x79,
(byte) 0xE7, (byte) 0xC8, (byte) 0x37, (byte) 0x6D, (byte) 0x8D, (byte) 0xD5, (byte) 0x4E, (byte) 0xA9,
(byte) 0x6C, (byte) 0x56, (byte) 0xF4, (byte) 0xEA, (byte) 0x65, (byte) 0x7A, (byte) 0xAE, (byte) 0x08,
(byte) 0xBA, (byte) 0x78, (byte) 0x25, (byte) 0x2E, (byte) 0x1C, (byte) 0xA6, (byte) 0xB4, (byte) 0xC6,
(byte) 0xE8, (byte) 0xDD, (byte) 0x74, (byte) 0x1F, (byte) 0x4B, (byte) 0xBD, (byte) 0x8B, (byte) 0x8A,
(byte) 0x70, (byte) 0x3E, (byte) 0xB5, (byte) 0x66, (byte) 0x48, (byte) 0x03, (byte) 0xF6, (byte) 0x0E,
(byte) 0x61, (byte) 0x35, (byte) 0x57, (byte) 0xB9, (byte) 0x86, (byte) 0xC1, (byte) 0x1D, (byte) 0x9E,
(byte) 0xE1, (byte) 0xF8, (byte) 0x98, (byte) 0x11, (byte) 0x69, (byte) 0xD9, (byte) 0x8E, (byte) 0x94,
(byte) 0x9B, (byte) 0x1E, (byte) 0x87, (byte) 0xE9, (byte) 0xCE, (byte) 0x55, (byte) 0x28, (byte) 0xDF,
(byte) 0x8C, (byte) 0xA1, (byte) 0x89, (byte) 0x0D, (byte) 0xBF, (byte) 0xE6, (byte) 0x42, (byte) 0x68,
(byte) 0x41, (byte) 0x99, (byte) 0x2D, (byte) 0x0F, (byte) 0xB0, (byte) 0x54, (byte) 0xBB, (byte) 0x16
};
/**
* S-box SQ.
*/
private static final byte[] SQ = {
(byte) 0x25, (byte) 0x24, (byte) 0x73, (byte) 0x67, (byte) 0xD7, (byte) 0xAE, (byte) 0x5C, (byte) 0x30,
(byte) 0xA4, (byte) 0xEE, (byte) 0x6E, (byte) 0xCB, (byte) 0x7D, (byte) 0xB5, (byte) 0x82, (byte) 0xDB,
(byte) 0xE4, (byte) 0x8E, (byte) 0x48, (byte) 0x49, (byte) 0x4F, (byte) 0x5D, (byte) 0x6A, (byte) 0x78,
(byte) 0x70, (byte) 0x88, (byte) 0xE8, (byte) 0x5F, (byte) 0x5E, (byte) 0x84, (byte) 0x65, (byte) 0xE2,
(byte) 0xD8, (byte) 0xE9, (byte) 0xCC, (byte) 0xED, (byte) 0x40, (byte) 0x2F, (byte) 0x11, (byte) 0x28,
(byte) 0x57, (byte) 0xD2, (byte) 0xAC, (byte) 0xE3, (byte) 0x4A, (byte) 0x15, (byte) 0x1B, (byte) 0xB9,
(byte) 0xB2, (byte) 0x80, (byte) 0x85, (byte) 0xA6, (byte) 0x2E, (byte) 0x02, (byte) 0x47, (byte) 0x29,
(byte) 0x07, (byte) 0x4B, (byte) 0x0E, (byte) 0xC1, (byte) 0x51, (byte) 0xAA, (byte) 0x89, (byte) 0xD4,
(byte) 0xCA, (byte) 0x01, (byte) 0x46, (byte) 0xB3, (byte) 0xEF, (byte) 0xDD, (byte) 0x44, (byte) 0x7B,
(byte) 0xC2, (byte) 0x7F, (byte) 0xBE, (byte) 0xC3, (byte) 0x9F, (byte) 0x20, (byte) 0x4C, (byte) 0x64,
(byte) 0x83, (byte) 0xA2, (byte) 0x68, (byte) 0x42, (byte) 0x13, (byte) 0xB4, (byte) 0x41, (byte) 0xCD,
(byte) 0xBA, (byte) 0xC6, (byte) 0xBB, (byte) 0x6D, (byte) 0x4D, (byte) 0x71, (byte) 0x21, (byte) 0xF4,
(byte) 0x8D, (byte) 0xB0, (byte) 0xE5, (byte) 0x93, (byte) 0xFE, (byte) 0x8F, (byte) 0xE6, (byte) 0xCF,
(byte) 0x43, (byte) 0x45, (byte) 0x31, (byte) 0x22, (byte) 0x37, (byte) 0x36, (byte) 0x96, (byte) 0xFA,
(byte) 0xBC, (byte) 0x0F, (byte) 0x08, (byte) 0x52, (byte) 0x1D, (byte) 0x55, (byte) 0x1A, (byte) 0xC5,
(byte) 0x4E, (byte) 0x23, (byte) 0x69, (byte) 0x7A, (byte) 0x92, (byte) 0xFF, (byte) 0x5B, (byte) 0x5A,
(byte) 0xEB, (byte) 0x9A, (byte) 0x1C, (byte) 0xA9, (byte) 0xD1, (byte) 0x7E, (byte) 0x0D, (byte) 0xFC,
(byte) 0x50, (byte) 0x8A, (byte) 0xB6, (byte) 0x62, (byte) 0xF5, (byte) 0x0A, (byte) 0xF8, (byte) 0xDC,
(byte) 0x03, (byte) 0x3C, (byte) 0x0C, (byte) 0x39, (byte) 0xF1, (byte) 0xB8, (byte) 0xF3, (byte) 0x3D,
(byte) 0xF2, (byte) 0xD5, (byte) 0x97, (byte) 0x66, (byte) 0x81, (byte) 0x32, (byte) 0xA0, (byte) 0x00,
(byte) 0x06, (byte) 0xCE, (byte) 0xF6, (byte) 0xEA, (byte) 0xB7, (byte) 0x17, (byte) 0xF7, (byte) 0x8C,
(byte) 0x79, (byte) 0xD6, (byte) 0xA7, (byte) 0xBF, (byte) 0x8B, (byte) 0x3F, (byte) 0x1F, (byte) 0x53,
(byte) 0x63, (byte) 0x75, (byte) 0x35, (byte) 0x2C, (byte) 0x60, (byte) 0xFD, (byte) 0x27, (byte) 0xD3,
(byte) 0x94, (byte) 0xA5, (byte) 0x7C, (byte) 0xA1, (byte) 0x05, (byte) 0x58, (byte) 0x2D, (byte) 0xBD,
(byte) 0xD9, (byte) 0xC7, (byte) 0xAF, (byte) 0x6B, (byte) 0x54, (byte) 0x0B, (byte) 0xE0, (byte) 0x38,
(byte) 0x04, (byte) 0xC8, (byte) 0x9D, (byte) 0xE7, (byte) 0x14, (byte) 0xB1, (byte) 0x87, (byte) 0x9C,
(byte) 0xDF, (byte) 0x6F, (byte) 0xF9, (byte) 0xDA, (byte) 0x2A, (byte) 0xC4, (byte) 0x59, (byte) 0x16,
(byte) 0x74, (byte) 0x91, (byte) 0xAB, (byte) 0x26, (byte) 0x61, (byte) 0x76, (byte) 0x34, (byte) 0x2B,
(byte) 0xAD, (byte) 0x99, (byte) 0xFB, (byte) 0x72, (byte) 0xEC, (byte) 0x33, (byte) 0x12, (byte) 0xDE,
(byte) 0x98, (byte) 0x3B, (byte) 0xC0, (byte) 0x9B, (byte) 0x3E, (byte) 0x18, (byte) 0x10, (byte) 0x3A,
(byte) 0x56, (byte) 0xE1, (byte) 0x77, (byte) 0xC9, (byte) 0x1E, (byte) 0x9E, (byte) 0x95, (byte) 0xA3,
(byte) 0x90, (byte) 0x19, (byte) 0xA8, (byte) 0x6C, (byte) 0x09, (byte) 0xD0, (byte) 0xF0, (byte) 0x86
};
/**
* LFSR State.
*/
private final int[] lfsrState = new int[16];
/**
* FSM State.
*/
private final int[] fsmState = new int[3];
/**
* index of next byte in keyStream.
*/
private int theIndex;
/**
* Advanced stream.
*/
private final byte[] keyStream = new byte[Integer.BYTES];
/**
* The iterations.
*/
private int theIterations;
/**
* Reset state.
*/
private GordianSnow3GEngine theResetState;
/**
* Constructor.
*/
public GordianSnow3GEngine() {
}
/**
* Constructor.
*
* @param pSource the source engine
*/
private GordianSnow3GEngine(final GordianSnow3GEngine pSource) {
reset(pSource);
}
/**
* initialise a Snow3G cipher.
*
* @param forEncryption whether or not we are for encryption.
* @param params the parameters required to set up the cipher.
* @throws IllegalArgumentException if the params argument is inappropriate.
*/
public void init(final boolean forEncryption,
final CipherParameters params) {
/*
* encryption and decryption is completely symmetrical, so the 'forEncryption' is
* irrelevant. (Like 90% of stream ciphers)
*/
/* Determine parameters */
CipherParameters myParams = params;
byte[] newKey = null;
byte[] newIV = null;
if ((myParams instanceof ParametersWithIV)) {
final ParametersWithIV ivParams = (ParametersWithIV) myParams;
newIV = ivParams.getIV();
myParams = ivParams.getParameters();
}
if (myParams instanceof KeyParameter) {
final KeyParameter keyParam = (KeyParameter) myParams;
newKey = keyParam.getKey();
}
/* Initialise engine and mark as initialised */
theIndex = 0;
theIterations = 0;
setKeyAndIV(newKey, newIV);
/* Save reset state */
theResetState = copy();
}
/**
* Obtain Max iterations.
*
* @return the maximum iterations
*/
protected int getMaxIterations() {
return 625;
}
@Override
public String getAlgorithmName() {
return "Snow3G";
}
@Override
public int processBytes(final byte[] in,
final int inOff,
final int len,
final byte[] out,
final int outOff) {
/* Check for errors */
if (theResetState == null) {
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 OutputLengthException("output buffer too short");
}
/* Loop through the input bytes */
for (int i = 0; i < len; i++) {
out[i + outOff] = returnByte(in[i + inOff]);
}
return len;
}
@Override
public void reset() {
if (theResetState != null) {
reset(theResetState);
}
}
@Override
public byte returnByte(final byte in) {
/* Make the keyStream if required */
if (theIndex == 0) {
makeKeyStream();
}
/* Map the next byte and adjust index */
final byte out = (byte) (keyStream[theIndex] ^ in);
theIndex = (theIndex + 1) % Integer.BYTES;
/* Return the mapped character */
return out;
}
/**
* Decode a 32-bit value from a buffer (little-endian).
*
* @param buf the input buffer
* @param off the input offset
* @return the decoded value
*/
private static int decode32be(final byte[] buf, final int off) {
return ((buf[off] & 0xFF) << 24)
| ((buf[off + 1] & 0xFF) << 16)
| ((buf[off + 2] & 0xFF) << 8)
| (buf[off + 3] & 0xFF);
}
/**
* Encode a 32-bit value into a buffer (little-endian).
*
* @param val the value to encode
* @param buf the output buffer
* @param off the output offset
*/
private static void encode32be(final int val, final byte[] buf, final int off) {
buf[off] = (byte) (val >> 24);
buf[off + 1] = (byte) (val >> 16);
buf[off + 2] = (byte) (val >> 8);
buf[off + 3] = (byte) (val);
}
/* MULx.
* Input v: an 8-bit input.
* Input c: an 8-bit input.
* Output : an 8-bit output.
* See section 3.1.1 for details.
*/
int mulX(final byte v, final int c) {
if ((v & 0x80) != 0) {
return ((v << 1) ^ c) & 0xFF;
} else {
return (v << 1) & 0xFF;
}
}
/* MULxPOW.
* Input v: an 8-bit input.
* Input i: a positive integer.
* Input c: an 8-bit input.
* Output : an 8-bit output.
* See section 3.1.2 for details.
*/
int mulXpow(final byte v, final int i, final int c) {
if (i == 0) {
return v & 0xFF;
} else {
return mulX((byte) mulXpow(v, i - 1, c), c);
}
}
/* The function MUL alpha.
* Input c: 8-bit input.
* Output : 32-bit output.
* See section 3.4.2 for details.
*/
int mulAlpha(final byte c) {
return ((mulXpow(c, 23, 0xa9) << 24)
| (mulXpow(c, 245, 0xa9) << 16)
| (mulXpow(c, 48, 0xa9) << 8)
| (mulXpow(c, 239, 0xa9)));
}
/* The function DIV alpha.
* Input c: 8-bit input.
* Output : 32-bit output.
* See section 3.4.3 for details.
*/
int divAlpha(final byte c) {
return ((mulXpow(c, 16, 0xa9) << 24)
| (mulXpow(c, 39, 0xa9) << 16)
| (mulXpow(c, 6, 0xa9) << 8)
| (mulXpow(c, 64, 0xa9)));
}
/* The 32x32-bit S-Box S1
* Input: a 32-bit input.
* Output: a 32-bit output of S1 box.
* See section 3.3.1.
*/
int s1(final int w) {
final byte srw0 = SR[((w >> 24) & 0xff)];
final byte srw1 = SR[((w >> 16) & 0xff)];
final byte srw2 = SR[((w >> 8) & 0xff)];
final byte srw3 = SR[((w) & 0xff)];
final int r0 = ((mulX(srw0, 0x1b))
^ (srw1)
^ (srw2)
^ ((mulX(srw3, 0x1b)) ^ srw3)
) & 0xFF;
final int r1 = (((mulX(srw0, 0x1b)) ^ srw0)
^ (mulX(srw1, 0x1b))
^ (srw2)
^ (srw3)
) & 0xFF;
final int r2 = ((srw0)
^ ((mulX(srw1, 0x1b)) ^ srw1)
^ (mulX(srw2, 0x1b))
^ (srw3)
) & 0xFF;
final int r3 = ((srw0)
^ (srw1)
^ ((mulX(srw2, 0x1b)) ^ srw2)
^ (mulX(srw3, 0x1b))
) & 0xFF;
return (((r0) << 24) | ((r1) << 16) | ((r2) << 8)
| (r3));
}
/* The 32x32-bit S-Box S2
* Input: a 32-bit input.
* Output: a 32-bit output of S2 box.
* See section 3.3.2.
*/
int s2(final int w) {
final byte sqw0 = SQ[((w >> 24) & 0xff)];
final byte sqw1 = SQ[((w >> 16) & 0xff)];
final byte sqw2 = SQ[((w >> 8) & 0xff)];
final byte sqw3 = SQ[((w) & 0xff)];
final int r0 = ((mulX(sqw0, 0x69))
^ (sqw1)
^ (sqw2)
^ ((mulX(sqw3, 0x69)) ^ sqw3)
) & 0xFF;
final int r1 = (((mulX(sqw0, 0x69)) ^ sqw0)
^ (mulX(sqw1, 0x69))
^ (sqw2)
^ (sqw3)
) & 0xFF;
final int r2 = ((sqw0)
^ ((mulX(sqw1, 0x69)) ^ sqw1)
^ (mulX(sqw2, 0x69))
^ (sqw3)
) & 0xFF;
final int r3 = ((sqw0)
^ (sqw1)
^ ((mulX(sqw2, 0x69)) ^ sqw2)
^ (mulX(sqw3, 0x69))
) & 0xFF;
return (((r0) << 24) | ((r1) << 16) | ((r2) << 8)
| (r3));
}
/* Clocking LFSR in initialization mode.
* LFSR Registers S0 to S15 are updated as the LFSR receives a single clock.
* Input f: a 32-bit word comes from output of FSM.
* See section 3.4.4.
*/
void clockLFSRInitializationMode(final int f) {
final int v = (((lfsrState[0] << 8) & 0xffffff00)
^ (mulAlpha((byte) ((lfsrState[0] >>> 24) & 0xff)))
^ (lfsrState[2])
^ ((lfsrState[11] >>> 8) & 0x00ffffff)
^ (divAlpha((byte) ((lfsrState[11]) & 0xff)))
^ (f)
);
lfsrState[0] = lfsrState[1];
lfsrState[1] = lfsrState[2];
lfsrState[2] = lfsrState[3];
lfsrState[3] = lfsrState[4];
lfsrState[4] = lfsrState[5];
lfsrState[5] = lfsrState[6];
lfsrState[6] = lfsrState[7];
lfsrState[7] = lfsrState[8];
lfsrState[8] = lfsrState[9];
lfsrState[9] = lfsrState[10];
lfsrState[10] = lfsrState[11];
lfsrState[11] = lfsrState[12];
lfsrState[12] = lfsrState[13];
lfsrState[13] = lfsrState[14];
lfsrState[14] = lfsrState[15];
lfsrState[15] = v;
}
/* Clocking LFSR in keystream mode.
* LFSR Registers S0 to S15 are updated as the LFSR receives a single clock.
* See section 3.4.5.
*/
void clockLFSRKeyStreamMode() {
final int v = (((lfsrState[0] << 8) & 0xffffff00)
^ (mulAlpha((byte) ((lfsrState[0] >>> 24) & 0xff)))
^ (lfsrState[2])
^ ((lfsrState[11] >>> 8) & 0x00ffffff)
^ (divAlpha((byte) ((lfsrState[11]) & 0xff)))
);
lfsrState[0] = lfsrState[1];
lfsrState[1] = lfsrState[2];
lfsrState[2] = lfsrState[3];
lfsrState[3] = lfsrState[4];
lfsrState[4] = lfsrState[5];
lfsrState[5] = lfsrState[6];
lfsrState[6] = lfsrState[7];
lfsrState[7] = lfsrState[8];
lfsrState[8] = lfsrState[9];
lfsrState[9] = lfsrState[10];
lfsrState[10] = lfsrState[11];
lfsrState[11] = lfsrState[12];
lfsrState[12] = lfsrState[13];
lfsrState[13] = lfsrState[14];
lfsrState[14] = lfsrState[15];
lfsrState[15] = v;
}
/* Clocking FSM.
* Produces a 32-bit word F.
* Updates FSM registers R1, R2, R3.
* See Section 3.4.6.
*/
int clockFSM() {
final int f = ((lfsrState[15] + fsmState[0]) & 0xffffffff) ^ fsmState[1];
final int r = (fsmState[1] + (fsmState[2] ^ lfsrState[5])) & 0xffffffff;
fsmState[2] = s2(fsmState[1]);
fsmState[1] = s1(fsmState[0]);
fsmState[0] = r;
return f;
}
/* Initialization.
* Input k[4]: Four 32-bit words making up 128-bit key.
* Input IV[4]: Four 32-bit words making 128-bit initialization variable.
* Output: All the LFSRs and FSM are initialized for key generation.
* See Section 4.1.
*/
void setKeyAndIV(final byte[] key, final byte[] iv) {
/* Check lengths */
if (key == null || key.length != 16) {
throw new IllegalArgumentException("A key of 16 bytes is needed");
}
if (iv == null || iv.length != 16) {
throw new IllegalArgumentException("An IV of 16 bytes is needed");
}
/* Generate four subkeys */
final int k0 = decode32be(key, 12);
final int k1 = decode32be(key, 8);
final int k2 = decode32be(key, 4);
final int k3 = decode32be(key, 0);
/* Generate four subvectors */
final int i0 = decode32be(iv, 12);
final int i1 = decode32be(iv, 8);
final int i2 = decode32be(iv, 4);
final int i3 = decode32be(iv, 0);
lfsrState[15] = k3 ^ i0;
lfsrState[14] = k2;
lfsrState[13] = k1;
lfsrState[12] = k0 ^ i1;
lfsrState[11] = k3 ^ 0xffffffff;
lfsrState[10] = k2 ^ 0xffffffff ^ i2;
lfsrState[9] = k1 ^ 0xffffffff ^ i3;
lfsrState[8] = k0 ^ 0xffffffff;
lfsrState[7] = k3;
lfsrState[6] = k2;
lfsrState[5] = k1;
lfsrState[4] = k0;
lfsrState[3] = k3 ^ 0xffffffff;
lfsrState[2] = k2 ^ 0xffffffff;
lfsrState[1] = k1 ^ 0xffffffff;
lfsrState[0] = k0 ^ 0xffffffff;
fsmState[0] = 0x0;
fsmState[1] = 0x0;
fsmState[2] = 0x0;
for (int i = 0; i < 32; i++) {
final int f = clockFSM();
clockLFSRInitializationMode(f);
}
/* Clock FSM once. Discard the output. */
clockFSM();
/* Clock LFSR in keystream mode once. */
clockLFSRKeyStreamMode();
}
/* Generation of Keystream.
* input n: number of 32-bit words of keystream.
* input z: space for the generated keystream, assumes
* memory is allocated already.
* output: generated keystream which is filled in z
* See section 4.2.
*/
void makeKeyStream() {
if (theIterations++ >= getMaxIterations()) {
throw new IllegalStateException("Too much data processed by singleKey/IV");
}
final int f = clockFSM(); // STEP 1 */
encode32be(f ^ lfsrState[0], keyStream, 0); // STEP 2 */
/* Note that ks[t] corresponds to z_{t+1} in section 4.2 */
clockLFSRKeyStreamMode(); // STEP 3 */
}
@Override
public GordianSnow3GEngine copy() {
return new GordianSnow3GEngine(this);
}
@Override
public void reset(final Memoable pState) {
final GordianSnow3GEngine e = (GordianSnow3GEngine) pState;
System.arraycopy(e.lfsrState, 0, lfsrState, 0, lfsrState.length);
System.arraycopy(e.fsmState, 0, fsmState, 0, fsmState.length);
System.arraycopy(e.keyStream, 0, keyStream, 0, keyStream.length);
theIterations = e.theIterations;
theIndex = e.theIndex;
}
}