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/*
* CAST-128
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/cast128.h>
#include <botan/loadstor.h>
#include <botan/rotate.h>
namespace Botan {
namespace {
/*
* CAST-128 Round Type 1
*/
inline void R1(u32bit& L, u32bit R, u32bit MK, u32bit RK)
{
u32bit T = rotate_left(MK + R, RK);
L ^= (CAST_SBOX1[get_byte(0, T)] ^ CAST_SBOX2[get_byte(1, T)]) -
CAST_SBOX3[get_byte(2, T)] + CAST_SBOX4[get_byte(3, T)];
}
/*
* CAST-128 Round Type 2
*/
inline void R2(u32bit& L, u32bit R, u32bit MK, u32bit RK)
{
u32bit T = rotate_left(MK ^ R, RK);
L ^= (CAST_SBOX1[get_byte(0, T)] - CAST_SBOX2[get_byte(1, T)] +
CAST_SBOX3[get_byte(2, T)]) ^ CAST_SBOX4[get_byte(3, T)];
}
/*
* CAST-128 Round Type 3
*/
inline void R3(u32bit& L, u32bit R, u32bit MK, u32bit RK)
{
u32bit T = rotate_left(MK - R, RK);
L ^= ((CAST_SBOX1[get_byte(0, T)] + CAST_SBOX2[get_byte(1, T)]) ^
CAST_SBOX3[get_byte(2, T)]) - CAST_SBOX4[get_byte(3, T)];
}
}
/*
* CAST-128 Encryption
*/
void CAST_128::encrypt_n(const byte in[], byte out[], size_t blocks) const
{
for(size_t i = 0; i != blocks; ++i)
{
u32bit L = load_be<u32bit>(in, 0);
u32bit R = load_be<u32bit>(in, 1);
R1(L, R, MK[ 0], RK[ 0]);
R2(R, L, MK[ 1], RK[ 1]);
R3(L, R, MK[ 2], RK[ 2]);
R1(R, L, MK[ 3], RK[ 3]);
R2(L, R, MK[ 4], RK[ 4]);
R3(R, L, MK[ 5], RK[ 5]);
R1(L, R, MK[ 6], RK[ 6]);
R2(R, L, MK[ 7], RK[ 7]);
R3(L, R, MK[ 8], RK[ 8]);
R1(R, L, MK[ 9], RK[ 9]);
R2(L, R, MK[10], RK[10]);
R3(R, L, MK[11], RK[11]);
R1(L, R, MK[12], RK[12]);
R2(R, L, MK[13], RK[13]);
R3(L, R, MK[14], RK[14]);
R1(R, L, MK[15], RK[15]);
store_be(out, R, L);
in += block_size();
out += block_size();
}
}
/*
* CAST-128 Decryption
*/
void CAST_128::decrypt_n(const byte in[], byte out[], size_t blocks) const
{
for(size_t i = 0; i != blocks; ++i)
{
u32bit L = load_be<u32bit>(in, 0);
u32bit R = load_be<u32bit>(in, 1);
R1(L, R, MK[15], RK[15]);
R3(R, L, MK[14], RK[14]);
R2(L, R, MK[13], RK[13]);
R1(R, L, MK[12], RK[12]);
R3(L, R, MK[11], RK[11]);
R2(R, L, MK[10], RK[10]);
R1(L, R, MK[ 9], RK[ 9]);
R3(R, L, MK[ 8], RK[ 8]);
R2(L, R, MK[ 7], RK[ 7]);
R1(R, L, MK[ 6], RK[ 6]);
R3(L, R, MK[ 5], RK[ 5]);
R2(R, L, MK[ 4], RK[ 4]);
R1(L, R, MK[ 3], RK[ 3]);
R3(R, L, MK[ 2], RK[ 2]);
R2(L, R, MK[ 1], RK[ 1]);
R1(R, L, MK[ 0], RK[ 0]);
store_be(out, R, L);
in += block_size();
out += block_size();
}
}
/*
* CAST-128 Key Schedule
*/
void CAST_128::key_schedule(const byte key[], size_t length)
{
clear();
SecureVector<u32bit> X(4);
for(size_t j = 0; j != length; ++j)
X[j/4] = (X[j/4] << 8) + key[j];
cast_ks(MK, X);
cast_ks(RK, X);
for(size_t j = 0; j != 16; ++j)
RK[j] %= 32;
}
/*
* S-Box Based Key Expansion
*/
void CAST_128::cast_ks(MemoryRegion<u32bit>& K,
MemoryRegion<u32bit>& X)
{
class ByteReader
{
public:
byte operator()(size_t i) { return (X[i/4] >> (8*(3 - (i%4)))); }
ByteReader(const u32bit* x) : X(x) {}
private:
const u32bit* X;
};
SecureVector<u32bit> Z(4);
ByteReader x(&X[0]), z(&Z[0]);
Z[0] = X[0] ^ S5[x(13)] ^ S6[x(15)] ^ S7[x(12)] ^ S8[x(14)] ^ S7[x( 8)];
Z[1] = X[2] ^ S5[z( 0)] ^ S6[z( 2)] ^ S7[z( 1)] ^ S8[z( 3)] ^ S8[x(10)];
Z[2] = X[3] ^ S5[z( 7)] ^ S6[z( 6)] ^ S7[z( 5)] ^ S8[z( 4)] ^ S5[x( 9)];
Z[3] = X[1] ^ S5[z(10)] ^ S6[z( 9)] ^ S7[z(11)] ^ S8[z( 8)] ^ S6[x(11)];
K[ 0] = S5[z( 8)] ^ S6[z( 9)] ^ S7[z( 7)] ^ S8[z( 6)] ^ S5[z( 2)];
K[ 1] = S5[z(10)] ^ S6[z(11)] ^ S7[z( 5)] ^ S8[z( 4)] ^ S6[z( 6)];
K[ 2] = S5[z(12)] ^ S6[z(13)] ^ S7[z( 3)] ^ S8[z( 2)] ^ S7[z( 9)];
K[ 3] = S5[z(14)] ^ S6[z(15)] ^ S7[z( 1)] ^ S8[z( 0)] ^ S8[z(12)];
X[0] = Z[2] ^ S5[z( 5)] ^ S6[z( 7)] ^ S7[z( 4)] ^ S8[z( 6)] ^ S7[z( 0)];
X[1] = Z[0] ^ S5[x( 0)] ^ S6[x( 2)] ^ S7[x( 1)] ^ S8[x( 3)] ^ S8[z( 2)];
X[2] = Z[1] ^ S5[x( 7)] ^ S6[x( 6)] ^ S7[x( 5)] ^ S8[x( 4)] ^ S5[z( 1)];
X[3] = Z[3] ^ S5[x(10)] ^ S6[x( 9)] ^ S7[x(11)] ^ S8[x( 8)] ^ S6[z( 3)];
K[ 4] = S5[x( 3)] ^ S6[x( 2)] ^ S7[x(12)] ^ S8[x(13)] ^ S5[x( 8)];
K[ 5] = S5[x( 1)] ^ S6[x( 0)] ^ S7[x(14)] ^ S8[x(15)] ^ S6[x(13)];
K[ 6] = S5[x( 7)] ^ S6[x( 6)] ^ S7[x( 8)] ^ S8[x( 9)] ^ S7[x( 3)];
K[ 7] = S5[x( 5)] ^ S6[x( 4)] ^ S7[x(10)] ^ S8[x(11)] ^ S8[x( 7)];
Z[0] = X[0] ^ S5[x(13)] ^ S6[x(15)] ^ S7[x(12)] ^ S8[x(14)] ^ S7[x( 8)];
Z[1] = X[2] ^ S5[z( 0)] ^ S6[z( 2)] ^ S7[z( 1)] ^ S8[z( 3)] ^ S8[x(10)];
Z[2] = X[3] ^ S5[z( 7)] ^ S6[z( 6)] ^ S7[z( 5)] ^ S8[z( 4)] ^ S5[x( 9)];
Z[3] = X[1] ^ S5[z(10)] ^ S6[z( 9)] ^ S7[z(11)] ^ S8[z( 8)] ^ S6[x(11)];
K[ 8] = S5[z( 3)] ^ S6[z( 2)] ^ S7[z(12)] ^ S8[z(13)] ^ S5[z( 9)];
K[ 9] = S5[z( 1)] ^ S6[z( 0)] ^ S7[z(14)] ^ S8[z(15)] ^ S6[z(12)];
K[10] = S5[z( 7)] ^ S6[z( 6)] ^ S7[z( 8)] ^ S8[z( 9)] ^ S7[z( 2)];
K[11] = S5[z( 5)] ^ S6[z( 4)] ^ S7[z(10)] ^ S8[z(11)] ^ S8[z( 6)];
X[0] = Z[2] ^ S5[z( 5)] ^ S6[z( 7)] ^ S7[z( 4)] ^ S8[z( 6)] ^ S7[z( 0)];
X[1] = Z[0] ^ S5[x( 0)] ^ S6[x( 2)] ^ S7[x( 1)] ^ S8[x( 3)] ^ S8[z( 2)];
X[2] = Z[1] ^ S5[x( 7)] ^ S6[x( 6)] ^ S7[x( 5)] ^ S8[x( 4)] ^ S5[z( 1)];
X[3] = Z[3] ^ S5[x(10)] ^ S6[x( 9)] ^ S7[x(11)] ^ S8[x( 8)] ^ S6[z( 3)];
K[12] = S5[x( 8)] ^ S6[x( 9)] ^ S7[x( 7)] ^ S8[x( 6)] ^ S5[x( 3)];
K[13] = S5[x(10)] ^ S6[x(11)] ^ S7[x( 5)] ^ S8[x( 4)] ^ S6[x( 7)];
K[14] = S5[x(12)] ^ S6[x(13)] ^ S7[x( 3)] ^ S8[x( 2)] ^ S7[x( 8)];
K[15] = S5[x(14)] ^ S6[x(15)] ^ S7[x( 1)] ^ S8[x( 0)] ^ S8[x(13)];
}
}
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