280 lines
9.8 KiB
C#
280 lines
9.8 KiB
C#
using System;
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using Org.BouncyCastle.Crypto.Utilities;
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namespace Org.BouncyCastle.Crypto.Engines
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{
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/**
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* A class that provides CAST6 key encryption operations,
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* such as encoding data and generating keys.
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*
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* All the algorithms herein are from the Internet RFC
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*
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* RFC2612 - CAST6 (128bit block, 128-256bit key)
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*
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* and implement a simplified cryptography interface.
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*/
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public sealed class Cast6Engine
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: Cast5Engine
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{
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//====================================
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// Useful constants
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//====================================
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private const int ROUNDS = 12;
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private const int BLOCK_SIZE = 16; // bytes = 128 bits
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/*
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* Put the round and mask keys into an array.
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* Kr0[i] => _Kr[i*4 + 0]
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*/
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private int []_Kr = new int[ROUNDS*4]; // the rotating round key(s)
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private uint []_Km = new uint[ROUNDS*4]; // the masking round key(s)
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/*
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* Key setup
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*/
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private int []_Tr = new int[24 * 8];
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private uint []_Tm = new uint[24 * 8];
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private uint[] _workingKey = new uint[8];
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public Cast6Engine()
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{
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}
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public override string AlgorithmName
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{
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get { return "CAST6"; }
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}
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public override void Reset()
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{
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}
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public override int GetBlockSize()
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{
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return BLOCK_SIZE;
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}
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//==================================
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// Private Implementation
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//==================================
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/*
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* Creates the subkeys using the same nomenclature
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* as described in RFC2612.
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*
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* See section 2.4
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*/
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internal override void SetKey(
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byte[] key)
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{
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uint Cm = 0x5a827999;
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uint Mm = 0x6ed9eba1;
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int Cr = 19;
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int Mr = 17;
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/*
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* Determine the key size here, if required
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*
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* if keysize < 256 bytes, pad with 0
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*
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* Typical key sizes => 128, 160, 192, 224, 256
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*/
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for (int i=0; i< 24; i++)
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{
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for (int j=0; j< 8; j++)
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{
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_Tm[i*8 + j] = Cm;
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Cm += Mm; //mod 2^32;
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_Tr[i*8 + j] = Cr;
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Cr = (Cr + Mr) & 0x1f; // mod 32
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}
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}
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byte[] tmpKey = new byte[64];
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key.CopyTo(tmpKey, 0);
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// now create ABCDEFGH
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for (int i = 0; i < 8; i++)
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{
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_workingKey[i] = Pack.BE_To_UInt32(tmpKey, i*4);
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}
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// Generate the key schedule
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for (int i = 0; i < 12; i++)
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{
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// KAPPA <- W2i(KAPPA)
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int i2 = i*2 *8;
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_workingKey[6] ^= F1(_workingKey[7], _Tm[i2], _Tr[i2]);
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_workingKey[5] ^= F2(_workingKey[6], _Tm[i2+1], _Tr[i2+1]);
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_workingKey[4] ^= F3(_workingKey[5], _Tm[i2+2], _Tr[i2+2]);
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_workingKey[3] ^= F1(_workingKey[4], _Tm[i2+3], _Tr[i2+3]);
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_workingKey[2] ^= F2(_workingKey[3], _Tm[i2+4], _Tr[i2+4]);
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_workingKey[1] ^= F3(_workingKey[2], _Tm[i2+5], _Tr[i2+5]);
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_workingKey[0] ^= F1(_workingKey[1], _Tm[i2+6], _Tr[i2+6]);
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_workingKey[7] ^= F2(_workingKey[0], _Tm[i2+7], _Tr[i2+7]);
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// KAPPA <- W2i+1(KAPPA)
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i2 = (i*2 + 1)*8;
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_workingKey[6] ^= F1(_workingKey[7], _Tm[i2], _Tr[i2]);
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_workingKey[5] ^= F2(_workingKey[6], _Tm[i2+1], _Tr[i2+1]);
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_workingKey[4] ^= F3(_workingKey[5], _Tm[i2+2], _Tr[i2+2]);
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_workingKey[3] ^= F1(_workingKey[4], _Tm[i2+3], _Tr[i2+3]);
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_workingKey[2] ^= F2(_workingKey[3], _Tm[i2+4], _Tr[i2+4]);
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_workingKey[1] ^= F3(_workingKey[2], _Tm[i2+5], _Tr[i2+5]);
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_workingKey[0] ^= F1(_workingKey[1], _Tm[i2+6], _Tr[i2+6]);
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_workingKey[7] ^= F2(_workingKey[0], _Tm[i2+7], _Tr[i2+7]);
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// Kr_(i) <- KAPPA
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_Kr[i*4] = (int)(_workingKey[0] & 0x1f);
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_Kr[i*4 + 1] = (int)(_workingKey[2] & 0x1f);
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_Kr[i*4 + 2] = (int)(_workingKey[4] & 0x1f);
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_Kr[i*4 + 3] = (int)(_workingKey[6] & 0x1f);
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// Km_(i) <- KAPPA
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_Km[i*4] = _workingKey[7];
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_Km[i*4 + 1] = _workingKey[5];
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_Km[i*4 + 2] = _workingKey[3];
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_Km[i*4 + 3] = _workingKey[1];
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}
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}
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/**
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* Encrypt the given input starting at the given offset and place
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* the result in the provided buffer starting at the given offset.
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*
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* @param src The plaintext buffer
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* @param srcIndex An offset into src
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* @param dst The ciphertext buffer
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* @param dstIndex An offset into dst
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*/
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internal override int EncryptBlock(
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byte[] src,
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int srcIndex,
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byte[] dst,
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int dstIndex)
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{
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// process the input block
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// batch the units up into 4x32 bit chunks and go for it
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uint A = Pack.BE_To_UInt32(src, srcIndex);
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uint B = Pack.BE_To_UInt32(src, srcIndex + 4);
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uint C = Pack.BE_To_UInt32(src, srcIndex + 8);
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uint D = Pack.BE_To_UInt32(src, srcIndex + 12);
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uint[] result = new uint[4];
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CAST_Encipher(A, B, C, D, result);
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// now stuff them into the destination block
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Pack.UInt32_To_BE(result[0], dst, dstIndex);
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Pack.UInt32_To_BE(result[1], dst, dstIndex + 4);
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Pack.UInt32_To_BE(result[2], dst, dstIndex + 8);
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Pack.UInt32_To_BE(result[3], dst, dstIndex + 12);
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return BLOCK_SIZE;
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}
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/**
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* Decrypt the given input starting at the given offset and place
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* the result in the provided buffer starting at the given offset.
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*
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* @param src The plaintext buffer
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* @param srcIndex An offset into src
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* @param dst The ciphertext buffer
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* @param dstIndex An offset into dst
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*/
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internal override int DecryptBlock(
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byte[] src,
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int srcIndex,
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byte[] dst,
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int dstIndex)
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{
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// process the input block
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// batch the units up into 4x32 bit chunks and go for it
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uint A = Pack.BE_To_UInt32(src, srcIndex);
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uint B = Pack.BE_To_UInt32(src, srcIndex + 4);
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uint C = Pack.BE_To_UInt32(src, srcIndex + 8);
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uint D = Pack.BE_To_UInt32(src, srcIndex + 12);
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uint[] result = new uint[4];
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CAST_Decipher(A, B, C, D, result);
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// now stuff them into the destination block
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Pack.UInt32_To_BE(result[0], dst, dstIndex);
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Pack.UInt32_To_BE(result[1], dst, dstIndex + 4);
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Pack.UInt32_To_BE(result[2], dst, dstIndex + 8);
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Pack.UInt32_To_BE(result[3], dst, dstIndex + 12);
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return BLOCK_SIZE;
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}
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/**
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* Does the 12 quad rounds rounds to encrypt the block.
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*
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* @param A the 00-31 bits of the plaintext block
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* @param B the 32-63 bits of the plaintext block
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* @param C the 64-95 bits of the plaintext block
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* @param D the 96-127 bits of the plaintext block
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* @param result the resulting ciphertext
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*/
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private void CAST_Encipher(
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uint A,
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uint B,
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uint C,
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uint D,
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uint[] result)
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{
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for (int i = 0; i < 6; i++)
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{
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int x = i*4;
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// BETA <- Qi(BETA)
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C ^= F1(D, _Km[x], _Kr[x]);
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B ^= F2(C, _Km[x + 1], _Kr[x + 1]);
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A ^= F3(B, _Km[x + 2], _Kr[x + 2]);
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D ^= F1(A, _Km[x + 3], _Kr[x + 3]);
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}
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for (int i = 6; i < 12; i++)
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{
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int x = i*4;
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// BETA <- QBARi(BETA)
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D ^= F1(A, _Km[x + 3], _Kr[x + 3]);
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A ^= F3(B, _Km[x + 2], _Kr[x + 2]);
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B ^= F2(C, _Km[x + 1], _Kr[x + 1]);
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C ^= F1(D, _Km[x], _Kr[x]);
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}
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result[0] = A;
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result[1] = B;
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result[2] = C;
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result[3] = D;
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}
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/**
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* Does the 12 quad rounds rounds to decrypt the block.
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*
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* @param A the 00-31 bits of the ciphertext block
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* @param B the 32-63 bits of the ciphertext block
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* @param C the 64-95 bits of the ciphertext block
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* @param D the 96-127 bits of the ciphertext block
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* @param result the resulting plaintext
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*/
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private void CAST_Decipher(
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uint A,
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uint B,
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uint C,
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uint D,
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uint[] result)
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{
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for (int i = 0; i < 6; i++)
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{
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int x = (11-i)*4;
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// BETA <- Qi(BETA)
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C ^= F1(D, _Km[x], _Kr[x]);
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B ^= F2(C, _Km[x + 1], _Kr[x + 1]);
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A ^= F3(B, _Km[x + 2], _Kr[x + 2]);
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D ^= F1(A, _Km[x + 3], _Kr[x + 3]);
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}
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for (int i=6; i<12; i++)
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{
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int x = (11-i)*4;
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// BETA <- QBARi(BETA)
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D ^= F1(A, _Km[x + 3], _Kr[x + 3]);
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A ^= F3(B, _Km[x + 2], _Kr[x + 2]);
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B ^= F2(C, _Km[x + 1], _Kr[x + 1]);
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C ^= F1(D, _Km[x], _Kr[x]);
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}
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result[0] = A;
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result[1] = B;
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result[2] = C;
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result[3] = D;
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}
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}
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}
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