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/*
* RC6
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/rc6.h>
#include <botan/loadstor.h>
#include <botan/rotate.h>
#include <algorithm>
namespace Botan {
/*
* RC6 Encryption
*/
void RC6::encrypt_n(const byte in[], byte out[], size_t blocks) const
{
for(size_t i = 0; i != blocks; ++i)
{
u32bit A = load_le<u32bit>(in, 0);
u32bit B = load_le<u32bit>(in, 1);
u32bit C = load_le<u32bit>(in, 2);
u32bit D = load_le<u32bit>(in, 3);
B += S[0]; D += S[1];
for(size_t j = 0; j != 20; j += 4)
{
u32bit T1, T2;
T1 = rotate_left(B*(2*B+1), 5);
T2 = rotate_left(D*(2*D+1), 5);
A = rotate_left(A ^ T1, T2 % 32) + S[2*j+2];
C = rotate_left(C ^ T2, T1 % 32) + S[2*j+3];
T1 = rotate_left(C*(2*C+1), 5);
T2 = rotate_left(A*(2*A+1), 5);
B = rotate_left(B ^ T1, T2 % 32) + S[2*j+4];
D = rotate_left(D ^ T2, T1 % 32) + S[2*j+5];
T1 = rotate_left(D*(2*D+1), 5);
T2 = rotate_left(B*(2*B+1), 5);
C = rotate_left(C ^ T1, T2 % 32) + S[2*j+6];
A = rotate_left(A ^ T2, T1 % 32) + S[2*j+7];
T1 = rotate_left(A*(2*A+1), 5);
T2 = rotate_left(C*(2*C+1), 5);
D = rotate_left(D ^ T1, T2 % 32) + S[2*j+8];
B = rotate_left(B ^ T2, T1 % 32) + S[2*j+9];
}
A += S[42]; C += S[43];
store_le(out, A, B, C, D);
in += BLOCK_SIZE;
out += BLOCK_SIZE;
}
}
/*
* RC6 Decryption
*/
void RC6::decrypt_n(const byte in[], byte out[], size_t blocks) const
{
for(size_t i = 0; i != blocks; ++i)
{
u32bit A = load_le<u32bit>(in, 0);
u32bit B = load_le<u32bit>(in, 1);
u32bit C = load_le<u32bit>(in, 2);
u32bit D = load_le<u32bit>(in, 3);
C -= S[43]; A -= S[42];
for(size_t j = 0; j != 20; j += 4)
{
u32bit T1, T2;
T1 = rotate_left(A*(2*A+1), 5);
T2 = rotate_left(C*(2*C+1), 5);
B = rotate_right(B - S[41 - 2*j], T1 % 32) ^ T2;
D = rotate_right(D - S[40 - 2*j], T2 % 32) ^ T1;
T1 = rotate_left(D*(2*D+1), 5);
T2 = rotate_left(B*(2*B+1), 5);
A = rotate_right(A - S[39 - 2*j], T1 % 32) ^ T2;
C = rotate_right(C - S[38 - 2*j], T2 % 32) ^ T1;
T1 = rotate_left(C*(2*C+1), 5);
T2 = rotate_left(A*(2*A+1), 5);
D = rotate_right(D - S[37 - 2*j], T1 % 32) ^ T2;
B = rotate_right(B - S[36 - 2*j], T2 % 32) ^ T1;
T1 = rotate_left(B*(2*B+1), 5);
T2 = rotate_left(D*(2*D+1), 5);
C = rotate_right(C - S[35 - 2*j], T1 % 32) ^ T2;
A = rotate_right(A - S[34 - 2*j], T2 % 32) ^ T1;
}
D -= S[1]; B -= S[0];
store_le(out, A, B, C, D);
in += BLOCK_SIZE;
out += BLOCK_SIZE;
}
}
/*
* RC6 Key Schedule
*/
void RC6::key_schedule(const byte key[], u32bit length)
{
const size_t WORD_KEYLENGTH = (((length - 1) / 4) + 1);
const size_t MIX_ROUNDS = 3 * std::max(WORD_KEYLENGTH, S.size());
S[0] = 0xB7E15163;
for(size_t j = 1; j != S.size(); ++j)
S[j] = S[j-1] + 0x9E3779B9;
SecureVector<u32bit> K(8);
for(s32bit j = length-1; j >= 0; --j)
K[j/4] = (K[j/4] << 8) + key[j];
u32bit A = 0, B = 0;
for(u32bit j = 0; j != MIX_ROUNDS; ++j)
{
A = rotate_left(S[j % S.size()] + A + B, 3);
B = rotate_left(K[j % WORD_KEYLENGTH] + A + B, (A + B) % 32);
S[j % S.size()] = A;
K[j % WORD_KEYLENGTH] = B;
}
}
}
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