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/*
* RC5
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/rc5.h>
#include <botan/loadstor.h>
#include <botan/rotate.h>
#include <botan/parsing.h>
#include <algorithm>
namespace Botan {
/*
* RC5 Encryption
*/
void RC5::encrypt_n(const byte in[], byte out[], size_t blocks) const
{
const size_t rounds = (S.size() - 2) / 2;
for(size_t i = 0; i != blocks; ++i)
{
u32bit A = load_le<u32bit>(in, 0);
u32bit B = load_le<u32bit>(in, 1);
A += S[0]; B += S[1];
for(size_t j = 0; j != rounds; j += 4)
{
A = rotate_left(A ^ B, B % 32) + S[2*j+2];
B = rotate_left(B ^ A, A % 32) + S[2*j+3];
A = rotate_left(A ^ B, B % 32) + S[2*j+4];
B = rotate_left(B ^ A, A % 32) + S[2*j+5];
A = rotate_left(A ^ B, B % 32) + S[2*j+6];
B = rotate_left(B ^ A, A % 32) + S[2*j+7];
A = rotate_left(A ^ B, B % 32) + S[2*j+8];
B = rotate_left(B ^ A, A % 32) + S[2*j+9];
}
store_le(out, A, B);
in += BLOCK_SIZE;
out += BLOCK_SIZE;
}
}
/*
* RC5 Decryption
*/
void RC5::decrypt_n(const byte in[], byte out[], size_t blocks) const
{
const size_t rounds = (S.size() - 2) / 2;
for(size_t i = 0; i != blocks; ++i)
{
u32bit A = load_le<u32bit>(in, 0);
u32bit B = load_le<u32bit>(in, 1);
for(size_t j = rounds; j != 0; j -= 4)
{
B = rotate_right(B - S[2*j+1], A % 32) ^ A;
A = rotate_right(A - S[2*j ], B % 32) ^ B;
B = rotate_right(B - S[2*j-1], A % 32) ^ A;
A = rotate_right(A - S[2*j-2], B % 32) ^ B;
B = rotate_right(B - S[2*j-3], A % 32) ^ A;
A = rotate_right(A - S[2*j-4], B % 32) ^ B;
B = rotate_right(B - S[2*j-5], A % 32) ^ A;
A = rotate_right(A - S[2*j-6], B % 32) ^ B;
}
B -= S[1]; A -= S[0];
store_le(out, A, B);
in += BLOCK_SIZE;
out += BLOCK_SIZE;
}
}
/*
* RC5 Key Schedule
*/
void RC5::key_schedule(const byte key[], size_t 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 i = 1; i != S.size(); ++i)
S[i] = S[i-1] + 0x9E3779B9;
SecureVector<u32bit> K(8);
for(s32bit i = length-1; i >= 0; --i)
K[i/4] = (K[i/4] << 8) + key[i];
u32bit A = 0, B = 0;
for(size_t i = 0; i != MIX_ROUNDS; ++i)
{
A = rotate_left(S[i % S.size()] + A + B, 3);
B = rotate_left(K[i % WORD_KEYLENGTH] + A + B, (A + B) % 32);
S[i % S.size()] = A;
K[i % WORD_KEYLENGTH] = B;
}
}
/*
* Return the name of this type
*/
std::string RC5::name() const
{
return "RC5(" + std::to_string(get_rounds()) + ")";
}
/*
* RC5 Constructor
*/
RC5::RC5(size_t rounds) : BlockCipher_Fixed_Block_Size(1, 32)
{
if(rounds < 8 || rounds > 32 || (rounds % 4 != 0))
throw Invalid_Argument("RC5: Invalid number of rounds " +
std::to_string(rounds));
S.resize(2*rounds + 2);
}
}
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