org.bouncycastle.crypto.engines.RC532Engine Maven / Gradle / Ivy
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package org.bouncycastle.crypto.engines; import org.bouncycastle.crypto.BlockCipher; import org.bouncycastle.crypto.CipherParameters; import org.bouncycastle.crypto.CryptoServicesRegistrar; import org.bouncycastle.crypto.constraints.DefaultServiceProperties; import org.bouncycastle.crypto.params.KeyParameter; import org.bouncycastle.crypto.params.RC5Parameters; /** * The specification for RC5 came from the RC5 Encryption Algorithm* publication in RSA CryptoBytes, Spring of 1995. * https://www.rsasecurity.com/rsalabs/cryptobytes. ** This implementation has a word size of 32 bits. */ public class RC532Engine implements BlockCipher { /* * the number of rounds to perform */ private int _noRounds; /* * the expanded key array of size 2*(rounds + 1) */ private int _S[]; /* * our "magic constants" for 32 32 * * Pw = Odd((e-2) * 2^wordsize) * Qw = Odd((o-2) * 2^wordsize) * * where e is the base of natural logarithms (2.718281828[]) * and o is the golden ratio (1.61803398[]) */ private static final int P32 = 0xb7e15163; private static final int Q32 = 0x9e3779b9; private boolean forEncryption; /** * Create an instance of the RC5 encryption algorithm * and set some defaults */ public RC532Engine() { _noRounds = 12; // the default _S = null; } public String getAlgorithmName() { return "RC5-32"; } public int getBlockSize() { return 2 * 4; } /** * initialise a RC5-32 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) { byte[] key; if (params instanceof RC5Parameters) { RC5Parameters p = (RC5Parameters)params; _noRounds = p.getRounds(); key = p.getKey(); setKey(key); } else if (params instanceof KeyParameter) { KeyParameter p = (KeyParameter)params; key = p.getKey(); setKey(key); } else { throw new IllegalArgumentException("invalid parameter passed to RC532 init - " + params.getClass().getName()); } this.forEncryption = forEncryption; CryptoServicesRegistrar.checkConstraints(new DefaultServiceProperties(getAlgorithmName(), key.length * 8, params, Utils.getPurpose(forEncryption))); } public int processBlock( byte[] in, int inOff, byte[] out, int outOff) { return (forEncryption) ? encryptBlock(in, inOff, out, outOff) : decryptBlock(in, inOff, out, outOff); } public void reset() { } /** * Re-key the cipher. *
* @param key the key to be used */ private void setKey( byte[] key) { // // KEY EXPANSION: // // There are 3 phases to the key expansion. // // Phase 1: // Copy the secret key K[0[]b-1] into an array L[0..c-1] of // c = ceil(b/u), where u = 32/8 in little-endian order. // In other words, we fill up L using u consecutive key bytes // of K. Any unfilled byte positions in L are zeroed. In the // case that b = c = 0, set c = 1 and L[0] = 0. // int[] L = new int[(key.length + (4 - 1)) / 4]; for (int i = 0; i != key.length; i++) { L[i / 4] += (key[i] & 0xff) << (8 * (i % 4)); } // // Phase 2: // Initialize S to a particular fixed pseudo-random bit pattern // using an arithmetic progression modulo 2^wordsize determined // by the magic numbers, Pw & Qw. // _S = new int[2*(_noRounds + 1)]; _S[0] = P32; for (int i=1; i < _S.length; i++) { _S[i] = (_S[i-1] + Q32); } // // Phase 3: // Mix in the user's secret key in 3 passes over the arrays S & L. // The max of the arrays sizes is used as the loop control // int iter; if (L.length > _S.length) { iter = 3 * L.length; } else { iter = 3 * _S.length; } int A = 0, B = 0; int i = 0, j = 0; for (int k = 0; k < iter; k++) { A = _S[i] = rotateLeft(_S[i] + A + B, 3); B = L[j] = rotateLeft(L[j] + A + B, A+B); i = (i+1) % _S.length; j = (j+1) % L.length; } } /** * Encrypt the given block starting at the given offset and place * the result in the provided buffer starting at the given offset. *
* @param in in byte buffer containing data to encrypt * @param inOff offset into src buffer * @param out out buffer where encrypted data is written * @param outOff offset into out buffer */ private int encryptBlock( byte[] in, int inOff, byte[] out, int outOff) { int A = bytesToWord(in, inOff) + _S[0]; int B = bytesToWord(in, inOff + 4) + _S[1]; for (int i = 1; i <= _noRounds; i++) { A = rotateLeft(A ^ B, B) + _S[2*i]; B = rotateLeft(B ^ A, A) + _S[2*i+1]; } wordToBytes(A, out, outOff); wordToBytes(B, out, outOff + 4); return 2 * 4; } private int decryptBlock( byte[] in, int inOff, byte[] out, int outOff) { int A = bytesToWord(in, inOff); int B = bytesToWord(in, inOff + 4); for (int i = _noRounds; i >= 1; i--) { B = rotateRight(B - _S[2*i+1], A) ^ A; A = rotateRight(A - _S[2*i], B) ^ B; } wordToBytes(A - _S[0], out, outOff); wordToBytes(B - _S[1], out, outOff + 4); return 2 * 4; } ////////////////////////////////////////////////////////////// // // PRIVATE Helper Methods // ////////////////////////////////////////////////////////////// /** * Perform a left "spin" of the word. The rotation of the given * word x is rotated left by y bits. * Only the lg(32) low-order bits of y * are used to determine the rotation amount. Here it is * assumed that the wordsize used is a power of 2. *
* @param x word to rotate * @param y number of bits to rotate % 32 */ private int rotateLeft(int x, int y) { return ((x << (y & (32-1))) | (x >>> (32 - (y & (32-1))))); } /** * Perform a right "spin" of the word. The rotation of the given * word x is rotated left by y bits. * Only the lg(32) low-order bits of y * are used to determine the rotation amount. Here it is * assumed that the wordsize used is a power of 2. *
* @param x word to rotate * @param y number of bits to rotate % 32 */ private int rotateRight(int x, int y) { return ((x >>> (y & (32-1))) | (x << (32 - (y & (32-1))))); } private int bytesToWord( byte[] src, int srcOff) { return (src[srcOff] & 0xff) | ((src[srcOff + 1] & 0xff) << 8) | ((src[srcOff + 2] & 0xff) << 16) | ((src[srcOff + 3] & 0xff) << 24); } private void wordToBytes( int word, byte[] dst, int dstOff) { dst[dstOff] = (byte)word; dst[dstOff + 1] = (byte)(word >> 8); dst[dstOff + 2] = (byte)(word >> 16); dst[dstOff + 3] = (byte)(word >> 24); } }