Java tutorial
package org.bouncycastle.crypto.engines; import org.bouncycastle.crypto.BlockCipher; import org.bouncycastle.crypto.CipherParameters; import org.bouncycastle.crypto.DataLengthException; import org.bouncycastle.crypto.OutputLengthException; import org.bouncycastle.crypto.params.KeyParameter; import org.bouncycastle.util.Pack; /** * an implementation of the AES (Rijndael), from FIPS-197. * <p> * For further details see: <a href="http://csrc.nist.gov/encryption/aes/">http://csrc.nist.gov/encryption/aes/</a>. * * This implementation is based on optimizations from Dr. Brian Gladman's paper and C code at * <a href="http://fp.gladman.plus.com/cryptography_technology/rijndael/">http://fp.gladman.plus.com/cryptography_technology/rijndael/</a> * * There are three levels of tradeoff of speed vs memory * Because java has no preprocessor, they are written as three separate classes from which to choose * * The fastest uses 8Kbytes of static tables to precompute round calculations, 4 256 word tables for encryption * and 4 for decryption. * * The middle performance version uses only one 256 word table for each, for a total of 2Kbytes, * adding 12 rotate operations per round to compute the values contained in the other tables from * the contents of the first * * The slowest version uses no static tables at all and computes the values * in each round. * <p> * This file contains the slowest performance version with no static tables * for round precomputation, but it has the smallest foot print. * */ public class AESLightEngine implements BlockCipher { // The S box private static final byte[] S = { (byte) 99, (byte) 124, (byte) 119, (byte) 123, (byte) 242, (byte) 107, (byte) 111, (byte) 197, (byte) 48, (byte) 1, (byte) 103, (byte) 43, (byte) 254, (byte) 215, (byte) 171, (byte) 118, (byte) 202, (byte) 130, (byte) 201, (byte) 125, (byte) 250, (byte) 89, (byte) 71, (byte) 240, (byte) 173, (byte) 212, (byte) 162, (byte) 175, (byte) 156, (byte) 164, (byte) 114, (byte) 192, (byte) 183, (byte) 253, (byte) 147, (byte) 38, (byte) 54, (byte) 63, (byte) 247, (byte) 204, (byte) 52, (byte) 165, (byte) 229, (byte) 241, (byte) 113, (byte) 216, (byte) 49, (byte) 21, (byte) 4, (byte) 199, (byte) 35, (byte) 195, (byte) 24, (byte) 150, (byte) 5, (byte) 154, (byte) 7, (byte) 18, (byte) 128, (byte) 226, (byte) 235, (byte) 39, (byte) 178, (byte) 117, (byte) 9, (byte) 131, (byte) 44, (byte) 26, (byte) 27, (byte) 110, (byte) 90, (byte) 160, (byte) 82, (byte) 59, (byte) 214, (byte) 179, (byte) 41, (byte) 227, (byte) 47, (byte) 132, (byte) 83, (byte) 209, (byte) 0, (byte) 237, (byte) 32, (byte) 252, (byte) 177, (byte) 91, (byte) 106, (byte) 203, (byte) 190, (byte) 57, (byte) 74, (byte) 76, (byte) 88, (byte) 207, (byte) 208, (byte) 239, (byte) 170, (byte) 251, (byte) 67, (byte) 77, (byte) 51, (byte) 133, (byte) 69, (byte) 249, (byte) 2, (byte) 127, (byte) 80, (byte) 60, (byte) 159, (byte) 168, (byte) 81, (byte) 163, (byte) 64, (byte) 143, (byte) 146, (byte) 157, (byte) 56, (byte) 245, (byte) 188, (byte) 182, (byte) 218, (byte) 33, (byte) 16, (byte) 255, (byte) 243, (byte) 210, (byte) 205, (byte) 12, (byte) 19, (byte) 236, (byte) 95, (byte) 151, (byte) 68, (byte) 23, (byte) 196, (byte) 167, (byte) 126, (byte) 61, (byte) 100, (byte) 93, (byte) 25, (byte) 115, (byte) 96, (byte) 129, (byte) 79, (byte) 220, (byte) 34, (byte) 42, (byte) 144, (byte) 136, (byte) 70, (byte) 238, (byte) 184, (byte) 20, (byte) 222, (byte) 94, (byte) 11, (byte) 219, (byte) 224, (byte) 50, (byte) 58, (byte) 10, (byte) 73, (byte) 6, (byte) 36, (byte) 92, (byte) 194, (byte) 211, (byte) 172, (byte) 98, (byte) 145, (byte) 149, (byte) 228, (byte) 121, (byte) 231, (byte) 200, (byte) 55, (byte) 109, (byte) 141, (byte) 213, (byte) 78, (byte) 169, (byte) 108, (byte) 86, (byte) 244, (byte) 234, (byte) 101, (byte) 122, (byte) 174, (byte) 8, (byte) 186, (byte) 120, (byte) 37, (byte) 46, (byte) 28, (byte) 166, (byte) 180, (byte) 198, (byte) 232, (byte) 221, (byte) 116, (byte) 31, (byte) 75, (byte) 189, (byte) 139, (byte) 138, (byte) 112, (byte) 62, (byte) 181, (byte) 102, (byte) 72, (byte) 3, (byte) 246, (byte) 14, (byte) 97, (byte) 53, (byte) 87, (byte) 185, (byte) 134, (byte) 193, (byte) 29, (byte) 158, (byte) 225, (byte) 248, (byte) 152, (byte) 17, (byte) 105, (byte) 217, (byte) 142, (byte) 148, (byte) 155, (byte) 30, (byte) 135, (byte) 233, (byte) 206, (byte) 85, (byte) 40, (byte) 223, (byte) 140, (byte) 161, (byte) 137, (byte) 13, (byte) 191, (byte) 230, (byte) 66, (byte) 104, (byte) 65, (byte) 153, (byte) 45, (byte) 15, (byte) 176, (byte) 84, (byte) 187, (byte) 22, }; // The inverse S-box private static final byte[] Si = { (byte) 82, (byte) 9, (byte) 106, (byte) 213, (byte) 48, (byte) 54, (byte) 165, (byte) 56, (byte) 191, (byte) 64, (byte) 163, (byte) 158, (byte) 129, (byte) 243, (byte) 215, (byte) 251, (byte) 124, (byte) 227, (byte) 57, (byte) 130, (byte) 155, (byte) 47, (byte) 255, (byte) 135, (byte) 52, (byte) 142, (byte) 67, (byte) 68, (byte) 196, (byte) 222, (byte) 233, (byte) 203, (byte) 84, (byte) 123, (byte) 148, (byte) 50, (byte) 166, (byte) 194, (byte) 35, (byte) 61, (byte) 238, (byte) 76, (byte) 149, (byte) 11, (byte) 66, (byte) 250, (byte) 195, (byte) 78, (byte) 8, (byte) 46, (byte) 161, (byte) 102, (byte) 40, (byte) 217, (byte) 36, (byte) 178, (byte) 118, (byte) 91, (byte) 162, (byte) 73, (byte) 109, (byte) 139, (byte) 209, (byte) 37, (byte) 114, (byte) 248, (byte) 246, (byte) 100, (byte) 134, (byte) 104, (byte) 152, (byte) 22, (byte) 212, (byte) 164, (byte) 92, (byte) 204, (byte) 93, (byte) 101, (byte) 182, (byte) 146, (byte) 108, (byte) 112, (byte) 72, (byte) 80, (byte) 253, (byte) 237, (byte) 185, (byte) 218, (byte) 94, (byte) 21, (byte) 70, (byte) 87, (byte) 167, (byte) 141, (byte) 157, (byte) 132, (byte) 144, (byte) 216, (byte) 171, (byte) 0, (byte) 140, (byte) 188, (byte) 211, (byte) 10, (byte) 247, (byte) 228, (byte) 88, (byte) 5, (byte) 184, (byte) 179, (byte) 69, (byte) 6, (byte) 208, (byte) 44, (byte) 30, (byte) 143, (byte) 202, (byte) 63, (byte) 15, (byte) 2, (byte) 193, (byte) 175, (byte) 189, (byte) 3, (byte) 1, (byte) 19, (byte) 138, (byte) 107, (byte) 58, (byte) 145, (byte) 17, (byte) 65, (byte) 79, (byte) 103, (byte) 220, (byte) 234, (byte) 151, (byte) 242, (byte) 207, (byte) 206, (byte) 240, (byte) 180, (byte) 230, (byte) 115, (byte) 150, (byte) 172, (byte) 116, (byte) 34, (byte) 231, (byte) 173, (byte) 53, (byte) 133, (byte) 226, (byte) 249, (byte) 55, (byte) 232, (byte) 28, (byte) 117, (byte) 223, (byte) 110, (byte) 71, (byte) 241, (byte) 26, (byte) 113, (byte) 29, (byte) 41, (byte) 197, (byte) 137, (byte) 111, (byte) 183, (byte) 98, (byte) 14, (byte) 170, (byte) 24, (byte) 190, (byte) 27, (byte) 252, (byte) 86, (byte) 62, (byte) 75, (byte) 198, (byte) 210, (byte) 121, (byte) 32, (byte) 154, (byte) 219, (byte) 192, (byte) 254, (byte) 120, (byte) 205, (byte) 90, (byte) 244, (byte) 31, (byte) 221, (byte) 168, (byte) 51, (byte) 136, (byte) 7, (byte) 199, (byte) 49, (byte) 177, (byte) 18, (byte) 16, (byte) 89, (byte) 39, (byte) 128, (byte) 236, (byte) 95, (byte) 96, (byte) 81, (byte) 127, (byte) 169, (byte) 25, (byte) 181, (byte) 74, (byte) 13, (byte) 45, (byte) 229, (byte) 122, (byte) 159, (byte) 147, (byte) 201, (byte) 156, (byte) 239, (byte) 160, (byte) 224, (byte) 59, (byte) 77, (byte) 174, (byte) 42, (byte) 245, (byte) 176, (byte) 200, (byte) 235, (byte) 187, (byte) 60, (byte) 131, (byte) 83, (byte) 153, (byte) 97, (byte) 23, (byte) 43, (byte) 4, (byte) 126, (byte) 186, (byte) 119, (byte) 214, (byte) 38, (byte) 225, (byte) 105, (byte) 20, (byte) 99, (byte) 85, (byte) 33, (byte) 12, (byte) 125, }; // vector used in calculating key schedule (powers of x in GF(256)) private static final int[] rcon = { 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91 }; private static int shift(int r, int shift) { return (r >>> shift) | (r << -shift); } /* multiply four bytes in GF(2^8) by 'x' {02} in parallel */ private static final int m1 = 0x80808080; private static final int m2 = 0x7f7f7f7f; private static final int m3 = 0x0000001b; private static final int m4 = 0xC0C0C0C0; private static final int m5 = 0x3f3f3f3f; private static int FFmulX(int x) { return (((x & m2) << 1) ^ (((x & m1) >>> 7) * m3)); } private static int FFmulX2(int x) { int t0 = (x & m5) << 2; int t1 = (x & m4); t1 ^= (t1 >>> 1); return t0 ^ (t1 >>> 2) ^ (t1 >>> 5); } /* The following defines provide alternative definitions of FFmulX that might give improved performance if a fast 32-bit multiply is not available. private int FFmulX(int x) { int u = x & m1; u |= (u >> 1); return ((x & m2) << 1) ^ ((u >>> 3) | (u >>> 6)); } private static final int m4 = 0x1b1b1b1b; private int FFmulX(int x) { int u = x & m1; return ((x & m2) << 1) ^ ((u - (u >>> 7)) & m4); } */ private static int mcol(int x) { int t0, t1; t0 = shift(x, 8); t1 = x ^ t0; return shift(t1, 16) ^ t0 ^ FFmulX(t1); } private static int inv_mcol(int x) { int t0, t1; t0 = x; t1 = t0 ^ shift(t0, 8); t0 ^= FFmulX(t1); t1 ^= FFmulX2(t0); t0 ^= t1 ^ shift(t1, 16); return t0; } private static int subWord(int x) { return (S[x & 255] & 255 | ((S[(x >> 8) & 255] & 255) << 8) | ((S[(x >> 16) & 255] & 255) << 16) | S[(x >> 24) & 255] << 24); } /** * Calculate the necessary round keys * The number of calculations depends on key size and block size * AES specified a fixed block size of 128 bits and key sizes 128/192/256 bits * This code is written assuming those are the only possible values */ private int[][] generateWorkingKey(byte[] key, boolean forEncryption) { int keyLen = key.length; if (keyLen < 16 || keyLen > 32 || (keyLen & 7) != 0) { throw new IllegalArgumentException("Key length not 128/192/256 bits."); } int KC = keyLen >> 2; ROUNDS = KC + 6; // This is not always true for the generalized Rijndael that allows larger block sizes int[][] W = new int[ROUNDS + 1][4]; // 4 words in a block switch (KC) { case 4: { int t0 = Pack.littleEndianToInt(key, 0); W[0][0] = t0; int t1 = Pack.littleEndianToInt(key, 4); W[0][1] = t1; int t2 = Pack.littleEndianToInt(key, 8); W[0][2] = t2; int t3 = Pack.littleEndianToInt(key, 12); W[0][3] = t3; for (int i = 1; i <= 10; ++i) { int u = subWord(shift(t3, 8)) ^ rcon[i - 1]; t0 ^= u; W[i][0] = t0; t1 ^= t0; W[i][1] = t1; t2 ^= t1; W[i][2] = t2; t3 ^= t2; W[i][3] = t3; } break; } case 6: { int t0 = Pack.littleEndianToInt(key, 0); W[0][0] = t0; int t1 = Pack.littleEndianToInt(key, 4); W[0][1] = t1; int t2 = Pack.littleEndianToInt(key, 8); W[0][2] = t2; int t3 = Pack.littleEndianToInt(key, 12); W[0][3] = t3; int t4 = Pack.littleEndianToInt(key, 16); W[1][0] = t4; int t5 = Pack.littleEndianToInt(key, 20); W[1][1] = t5; int rcon = 1; int u = subWord(shift(t5, 8)) ^ rcon; rcon <<= 1; t0 ^= u; W[1][2] = t0; t1 ^= t0; W[1][3] = t1; t2 ^= t1; W[2][0] = t2; t3 ^= t2; W[2][1] = t3; t4 ^= t3; W[2][2] = t4; t5 ^= t4; W[2][3] = t5; for (int i = 3; i < 12; i += 3) { u = subWord(shift(t5, 8)) ^ rcon; rcon <<= 1; t0 ^= u; W[i][0] = t0; t1 ^= t0; W[i][1] = t1; t2 ^= t1; W[i][2] = t2; t3 ^= t2; W[i][3] = t3; t4 ^= t3; W[i + 1][0] = t4; t5 ^= t4; W[i + 1][1] = t5; u = subWord(shift(t5, 8)) ^ rcon; rcon <<= 1; t0 ^= u; W[i + 1][2] = t0; t1 ^= t0; W[i + 1][3] = t1; t2 ^= t1; W[i + 2][0] = t2; t3 ^= t2; W[i + 2][1] = t3; t4 ^= t3; W[i + 2][2] = t4; t5 ^= t4; W[i + 2][3] = t5; } u = subWord(shift(t5, 8)) ^ rcon; t0 ^= u; W[12][0] = t0; t1 ^= t0; W[12][1] = t1; t2 ^= t1; W[12][2] = t2; t3 ^= t2; W[12][3] = t3; break; } case 8: { int t0 = Pack.littleEndianToInt(key, 0); W[0][0] = t0; int t1 = Pack.littleEndianToInt(key, 4); W[0][1] = t1; int t2 = Pack.littleEndianToInt(key, 8); W[0][2] = t2; int t3 = Pack.littleEndianToInt(key, 12); W[0][3] = t3; int t4 = Pack.littleEndianToInt(key, 16); W[1][0] = t4; int t5 = Pack.littleEndianToInt(key, 20); W[1][1] = t5; int t6 = Pack.littleEndianToInt(key, 24); W[1][2] = t6; int t7 = Pack.littleEndianToInt(key, 28); W[1][3] = t7; int u, rcon = 1; for (int i = 2; i < 14; i += 2) { u = subWord(shift(t7, 8)) ^ rcon; rcon <<= 1; t0 ^= u; W[i][0] = t0; t1 ^= t0; W[i][1] = t1; t2 ^= t1; W[i][2] = t2; t3 ^= t2; W[i][3] = t3; u = subWord(t3); t4 ^= u; W[i + 1][0] = t4; t5 ^= t4; W[i + 1][1] = t5; t6 ^= t5; W[i + 1][2] = t6; t7 ^= t6; W[i + 1][3] = t7; } u = subWord(shift(t7, 8)) ^ rcon; t0 ^= u; W[14][0] = t0; t1 ^= t0; W[14][1] = t1; t2 ^= t1; W[14][2] = t2; t3 ^= t2; W[14][3] = t3; break; } default: { throw new IllegalStateException("Should never get here"); } } if (!forEncryption) { for (int j = 1; j < ROUNDS; j++) { for (int i = 0; i < 4; i++) { W[j][i] = inv_mcol(W[j][i]); } } } return W; } private int ROUNDS; private int[][] WorkingKey = null; private int C0, C1, C2, C3; private boolean forEncryption; private static final int BLOCK_SIZE = 16; /** * default constructor - 128 bit block size. */ public AESLightEngine() { } /** * initialise an AES 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) { WorkingKey = generateWorkingKey(((KeyParameter) params).getKey(), forEncryption); this.forEncryption = forEncryption; return; } throw new IllegalArgumentException("invalid parameter passed to AES init - " + params.getClass().getName()); } public String getAlgorithmName() { return "AES"; } public int getBlockSize() { return BLOCK_SIZE; } public int processBlock(byte[] in, int inOff, byte[] out, int outOff) { if (WorkingKey == null) { throw new IllegalStateException("AES engine not initialised"); } if ((inOff + (32 / 2)) > in.length) { throw new DataLengthException("input buffer too short"); } if ((outOff + (32 / 2)) > out.length) { throw new OutputLengthException("output buffer too short"); } if (forEncryption) { unpackBlock(in, inOff); encryptBlock(WorkingKey); packBlock(out, outOff); } else { unpackBlock(in, inOff); decryptBlock(WorkingKey); packBlock(out, outOff); } return BLOCK_SIZE; } public void reset() { } private void unpackBlock(byte[] bytes, int off) { int index = off; C0 = (bytes[index++] & 0xff); C0 |= (bytes[index++] & 0xff) << 8; C0 |= (bytes[index++] & 0xff) << 16; C0 |= bytes[index++] << 24; C1 = (bytes[index++] & 0xff); C1 |= (bytes[index++] & 0xff) << 8; C1 |= (bytes[index++] & 0xff) << 16; C1 |= bytes[index++] << 24; C2 = (bytes[index++] & 0xff); C2 |= (bytes[index++] & 0xff) << 8; C2 |= (bytes[index++] & 0xff) << 16; C2 |= bytes[index++] << 24; C3 = (bytes[index++] & 0xff); C3 |= (bytes[index++] & 0xff) << 8; C3 |= (bytes[index++] & 0xff) << 16; C3 |= bytes[index++] << 24; } private void packBlock(byte[] bytes, int off) { int index = off; bytes[index++] = (byte) C0; bytes[index++] = (byte) (C0 >> 8); bytes[index++] = (byte) (C0 >> 16); bytes[index++] = (byte) (C0 >> 24); bytes[index++] = (byte) C1; bytes[index++] = (byte) (C1 >> 8); bytes[index++] = (byte) (C1 >> 16); bytes[index++] = (byte) (C1 >> 24); bytes[index++] = (byte) C2; bytes[index++] = (byte) (C2 >> 8); bytes[index++] = (byte) (C2 >> 16); bytes[index++] = (byte) (C2 >> 24); bytes[index++] = (byte) C3; bytes[index++] = (byte) (C3 >> 8); bytes[index++] = (byte) (C3 >> 16); bytes[index++] = (byte) (C3 >> 24); } private void encryptBlock(int[][] KW) { int t0 = this.C0 ^ KW[0][0]; int t1 = this.C1 ^ KW[0][1]; int t2 = this.C2 ^ KW[0][2]; int r = 1, r0, r1, r2, r3 = this.C3 ^ KW[0][3]; while (r < ROUNDS - 1) { r0 = mcol((S[t0 & 255] & 255) ^ ((S[(t1 >> 8) & 255] & 255) << 8) ^ ((S[(t2 >> 16) & 255] & 255) << 16) ^ (S[(r3 >> 24) & 255] << 24)) ^ KW[r][0]; r1 = mcol((S[t1 & 255] & 255) ^ ((S[(t2 >> 8) & 255] & 255) << 8) ^ ((S[(r3 >> 16) & 255] & 255) << 16) ^ (S[(t0 >> 24) & 255] << 24)) ^ KW[r][1]; r2 = mcol((S[t2 & 255] & 255) ^ ((S[(r3 >> 8) & 255] & 255) << 8) ^ ((S[(t0 >> 16) & 255] & 255) << 16) ^ (S[(t1 >> 24) & 255] << 24)) ^ KW[r][2]; r3 = mcol((S[r3 & 255] & 255) ^ ((S[(t0 >> 8) & 255] & 255) << 8) ^ ((S[(t1 >> 16) & 255] & 255) << 16) ^ (S[(t2 >> 24) & 255] << 24)) ^ KW[r++][3]; t0 = mcol((S[r0 & 255] & 255) ^ ((S[(r1 >> 8) & 255] & 255) << 8) ^ ((S[(r2 >> 16) & 255] & 255) << 16) ^ (S[(r3 >> 24) & 255] << 24)) ^ KW[r][0]; t1 = mcol((S[r1 & 255] & 255) ^ ((S[(r2 >> 8) & 255] & 255) << 8) ^ ((S[(r3 >> 16) & 255] & 255) << 16) ^ (S[(r0 >> 24) & 255] << 24)) ^ KW[r][1]; t2 = mcol((S[r2 & 255] & 255) ^ ((S[(r3 >> 8) & 255] & 255) << 8) ^ ((S[(r0 >> 16) & 255] & 255) << 16) ^ (S[(r1 >> 24) & 255] << 24)) ^ KW[r][2]; r3 = mcol((S[r3 & 255] & 255) ^ ((S[(r0 >> 8) & 255] & 255) << 8) ^ ((S[(r1 >> 16) & 255] & 255) << 16) ^ (S[(r2 >> 24) & 255] << 24)) ^ KW[r++][3]; } r0 = mcol((S[t0 & 255] & 255) ^ ((S[(t1 >> 8) & 255] & 255) << 8) ^ ((S[(t2 >> 16) & 255] & 255) << 16) ^ (S[(r3 >> 24) & 255] << 24)) ^ KW[r][0]; r1 = mcol((S[t1 & 255] & 255) ^ ((S[(t2 >> 8) & 255] & 255) << 8) ^ ((S[(r3 >> 16) & 255] & 255) << 16) ^ (S[(t0 >> 24) & 255] << 24)) ^ KW[r][1]; r2 = mcol((S[t2 & 255] & 255) ^ ((S[(r3 >> 8) & 255] & 255) << 8) ^ ((S[(t0 >> 16) & 255] & 255) << 16) ^ (S[(t1 >> 24) & 255] << 24)) ^ KW[r][2]; r3 = mcol((S[r3 & 255] & 255) ^ ((S[(t0 >> 8) & 255] & 255) << 8) ^ ((S[(t1 >> 16) & 255] & 255) << 16) ^ (S[(t2 >> 24) & 255] << 24)) ^ KW[r++][3]; // the final round is a simple function of S this.C0 = (S[r0 & 255] & 255) ^ ((S[(r1 >> 8) & 255] & 255) << 8) ^ ((S[(r2 >> 16) & 255] & 255) << 16) ^ (S[(r3 >> 24) & 255] << 24) ^ KW[r][0]; this.C1 = (S[r1 & 255] & 255) ^ ((S[(r2 >> 8) & 255] & 255) << 8) ^ ((S[(r3 >> 16) & 255] & 255) << 16) ^ (S[(r0 >> 24) & 255] << 24) ^ KW[r][1]; this.C2 = (S[r2 & 255] & 255) ^ ((S[(r3 >> 8) & 255] & 255) << 8) ^ ((S[(r0 >> 16) & 255] & 255) << 16) ^ (S[(r1 >> 24) & 255] << 24) ^ KW[r][2]; this.C3 = (S[r3 & 255] & 255) ^ ((S[(r0 >> 8) & 255] & 255) << 8) ^ ((S[(r1 >> 16) & 255] & 255) << 16) ^ (S[(r2 >> 24) & 255] << 24) ^ KW[r][3]; } private void decryptBlock(int[][] KW) { int t0 = this.C0 ^ KW[ROUNDS][0]; int t1 = this.C1 ^ KW[ROUNDS][1]; int t2 = this.C2 ^ KW[ROUNDS][2]; int r = ROUNDS - 1, r0, r1, r2, r3 = this.C3 ^ KW[ROUNDS][3]; while (r > 1) { r0 = inv_mcol((Si[t0 & 255] & 255) ^ ((Si[(r3 >> 8) & 255] & 255) << 8) ^ ((Si[(t2 >> 16) & 255] & 255) << 16) ^ (Si[(t1 >> 24) & 255] << 24)) ^ KW[r][0]; r1 = inv_mcol((Si[t1 & 255] & 255) ^ ((Si[(t0 >> 8) & 255] & 255) << 8) ^ ((Si[(r3 >> 16) & 255] & 255) << 16) ^ (Si[(t2 >> 24) & 255] << 24)) ^ KW[r][1]; r2 = inv_mcol((Si[t2 & 255] & 255) ^ ((Si[(t1 >> 8) & 255] & 255) << 8) ^ ((Si[(t0 >> 16) & 255] & 255) << 16) ^ (Si[(r3 >> 24) & 255] << 24)) ^ KW[r][2]; r3 = inv_mcol((Si[r3 & 255] & 255) ^ ((Si[(t2 >> 8) & 255] & 255) << 8) ^ ((Si[(t1 >> 16) & 255] & 255) << 16) ^ (Si[(t0 >> 24) & 255] << 24)) ^ KW[r--][3]; t0 = inv_mcol((Si[r0 & 255] & 255) ^ ((Si[(r3 >> 8) & 255] & 255) << 8) ^ ((Si[(r2 >> 16) & 255] & 255) << 16) ^ (Si[(r1 >> 24) & 255] << 24)) ^ KW[r][0]; t1 = inv_mcol((Si[r1 & 255] & 255) ^ ((Si[(r0 >> 8) & 255] & 255) << 8) ^ ((Si[(r3 >> 16) & 255] & 255) << 16) ^ (Si[(r2 >> 24) & 255] << 24)) ^ KW[r][1]; t2 = inv_mcol((Si[r2 & 255] & 255) ^ ((Si[(r1 >> 8) & 255] & 255) << 8) ^ ((Si[(r0 >> 16) & 255] & 255) << 16) ^ (Si[(r3 >> 24) & 255] << 24)) ^ KW[r][2]; r3 = inv_mcol((Si[r3 & 255] & 255) ^ ((Si[(r2 >> 8) & 255] & 255) << 8) ^ ((Si[(r1 >> 16) & 255] & 255) << 16) ^ (Si[(r0 >> 24) & 255] << 24)) ^ KW[r--][3]; } r0 = inv_mcol((Si[t0 & 255] & 255) ^ ((Si[(r3 >> 8) & 255] & 255) << 8) ^ ((Si[(t2 >> 16) & 255] & 255) << 16) ^ (Si[(t1 >> 24) & 255] << 24)) ^ KW[r][0]; r1 = inv_mcol((Si[t1 & 255] & 255) ^ ((Si[(t0 >> 8) & 255] & 255) << 8) ^ ((Si[(r3 >> 16) & 255] & 255) << 16) ^ (Si[(t2 >> 24) & 255] << 24)) ^ KW[r][1]; r2 = inv_mcol((Si[t2 & 255] & 255) ^ ((Si[(t1 >> 8) & 255] & 255) << 8) ^ ((Si[(t0 >> 16) & 255] & 255) << 16) ^ (Si[(r3 >> 24) & 255] << 24)) ^ KW[r][2]; r3 = inv_mcol((Si[r3 & 255] & 255) ^ ((Si[(t2 >> 8) & 255] & 255) << 8) ^ ((Si[(t1 >> 16) & 255] & 255) << 16) ^ (Si[(t0 >> 24) & 255] << 24)) ^ KW[r][3]; // the final round's table is a simple function of Si this.C0 = (Si[r0 & 255] & 255) ^ ((Si[(r3 >> 8) & 255] & 255) << 8) ^ ((Si[(r2 >> 16) & 255] & 255) << 16) ^ (Si[(r1 >> 24) & 255] << 24) ^ KW[0][0]; this.C1 = (Si[r1 & 255] & 255) ^ ((Si[(r0 >> 8) & 255] & 255) << 8) ^ ((Si[(r3 >> 16) & 255] & 255) << 16) ^ (Si[(r2 >> 24) & 255] << 24) ^ KW[0][1]; this.C2 = (Si[r2 & 255] & 255) ^ ((Si[(r1 >> 8) & 255] & 255) << 8) ^ ((Si[(r0 >> 16) & 255] & 255) << 16) ^ (Si[(r3 >> 24) & 255] << 24) ^ KW[0][2]; this.C3 = (Si[r3 & 255] & 255) ^ ((Si[(r2 >> 8) & 255] & 255) << 8) ^ ((Si[(r1 >> 16) & 255] & 255) << 16) ^ (Si[(r0 >> 24) & 255] << 24) ^ KW[0][3]; } }