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/* cast128.c
*
* The CAST-128 block cipher, described in RFC 2144.
*/
/* CAST-128 in C
* Written by Steve Reid <sreid@sea-to-sky.net>
* 100% Public Domain - no warranty
* Released 1997.10.11
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2001 Niels Möller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#include "cast128.h"
#include "cast128_sboxes.h"
#include "macros.h"
#include <assert.h>
#define CAST_SMALL_KEY 10
#define CAST_SMALL_ROUNDS 12
#define CAST_FULL_ROUNDS 16
/* Macros to access 8-bit bytes out of a 32-bit word */
#define U8a(x) ( (uint8_t) (x>>24) )
#define U8b(x) ( (uint8_t) ((x>>16)&0xff) )
#define U8c(x) ( (uint8_t) ((x>>8)&0xff) )
#define U8d(x) ( (uint8_t) ((x)&0xff) )
/* Circular left shift */
#define ROL(x, n) ( ((x)<<(n)) | ((x)>>(32-(n))) )
/* CAST-128 uses three different round functions */
#define F1(l, r, i) \
t = ROL(ctx->keys[i] + r, ctx->keys[i+16]); \
l ^= ((cast_sbox1[U8a(t)] ^ cast_sbox2[U8b(t)]) \
- cast_sbox3[U8c(t)]) + cast_sbox4[U8d(t)];
#define F2(l, r, i) \
t = ROL(ctx->keys[i] ^ r, ctx->keys[i+16]); \
l ^= ((cast_sbox1[U8a(t)] - cast_sbox2[U8b(t)]) \
+ cast_sbox3[U8c(t)]) ^ cast_sbox4[U8d(t)];
#define F3(l, r, i) \
t = ROL(ctx->keys[i] - r, ctx->keys[i+16]); \
l ^= ((cast_sbox1[U8a(t)] + cast_sbox2[U8b(t)]) \
^ cast_sbox3[U8c(t)]) - cast_sbox4[U8d(t)];
/***** Encryption Function *****/
void
cast128_encrypt(struct cast128_ctx *ctx,
unsigned length, uint8_t *dst,
const uint8_t *src)
{
FOR_BLOCKS(length, dst, src, CAST128_BLOCK_SIZE)
{
uint32_t t, l, r;
/* Get inblock into l,r */
l = READ_UINT32(src);
r = READ_UINT32(src+4);
/* Do the work */
F1(l, r, 0);
F2(r, l, 1);
F3(l, r, 2);
F1(r, l, 3);
F2(l, r, 4);
F3(r, l, 5);
F1(l, r, 6);
F2(r, l, 7);
F3(l, r, 8);
F1(r, l, 9);
F2(l, r, 10);
F3(r, l, 11);
/* Only do full 16 rounds if key length > 80 bits */
if (ctx->rounds > 12) {
F1(l, r, 12);
F2(r, l, 13);
F3(l, r, 14);
F1(r, l, 15);
}
/* Put l,r into outblock */
WRITE_UINT32(dst, r);
WRITE_UINT32(dst + 4, l);
/* Wipe clean */
t = l = r = 0;
}
}
/***** Decryption Function *****/
void
cast128_decrypt(struct cast128_ctx *ctx,
unsigned length, uint8_t *dst,
const uint8_t *src)
{
FOR_BLOCKS(length, dst, src, CAST128_BLOCK_SIZE)
{
uint32_t t, l, r;
/* Get inblock into l,r */
r = READ_UINT32(src);
l = READ_UINT32(src+4);
/* Do the work */
/* Only do full 16 rounds if key length > 80 bits */
if (ctx->rounds > 12) {
F1(r, l, 15);
F3(l, r, 14);
F2(r, l, 13);
F1(l, r, 12);
}
F3(r, l, 11);
F2(l, r, 10);
F1(r, l, 9);
F3(l, r, 8);
F2(r, l, 7);
F1(l, r, 6);
F3(r, l, 5);
F2(l, r, 4);
F1(r, l, 3);
F3(l, r, 2);
F2(r, l, 1);
F1(l, r, 0);
/* Put l,r into outblock */
WRITE_UINT32(dst, l);
WRITE_UINT32(dst + 4, r);
/* Wipe clean */
t = l = r = 0;
}
}
/***** Key Schedule *****/
void
cast128_set_key(struct cast128_ctx *ctx,
unsigned keybytes, const uint8_t *rawkey)
{
uint32_t t[4], z[4], x[4];
unsigned i;
/* Set number of rounds to 12 or 16, depending on key length */
ctx->rounds = (keybytes <= CAST_SMALL_KEY)
? CAST_SMALL_ROUNDS : CAST_FULL_ROUNDS;
/* Copy key to workspace x */
for (i = 0; i < 4; i++) {
x[i] = 0;
if ((i*4+0) < keybytes) x[i] = (uint32_t)rawkey[i*4+0] << 24;
if ((i*4+1) < keybytes) x[i] |= (uint32_t)rawkey[i*4+1] << 16;
if ((i*4+2) < keybytes) x[i] |= (uint32_t)rawkey[i*4+2] << 8;
if ((i*4+3) < keybytes) x[i] |= (uint32_t)rawkey[i*4+3];
}
/* Generate 32 subkeys, four at a time */
for (i = 0; i < 32; i+=4) {
switch (i & 4) {
case 0:
t[0] = z[0] = x[0] ^ cast_sbox5[U8b(x[3])]
^ cast_sbox6[U8d(x[3])] ^ cast_sbox7[U8a(x[3])]
^ cast_sbox8[U8c(x[3])] ^ cast_sbox7[U8a(x[2])];
t[1] = z[1] = x[2] ^ cast_sbox5[U8a(z[0])]
^ cast_sbox6[U8c(z[0])] ^ cast_sbox7[U8b(z[0])]
^ cast_sbox8[U8d(z[0])] ^ cast_sbox8[U8c(x[2])];
t[2] = z[2] = x[3] ^ cast_sbox5[U8d(z[1])]
^ cast_sbox6[U8c(z[1])] ^ cast_sbox7[U8b(z[1])]
^ cast_sbox8[U8a(z[1])] ^ cast_sbox5[U8b(x[2])];
t[3] = z[3] = x[1] ^ cast_sbox5[U8c(z[2])] ^
cast_sbox6[U8b(z[2])] ^ cast_sbox7[U8d(z[2])]
^ cast_sbox8[U8a(z[2])] ^ cast_sbox6[U8d(x[2])];
break;
case 4:
t[0] = x[0] = z[2] ^ cast_sbox5[U8b(z[1])]
^ cast_sbox6[U8d(z[1])] ^ cast_sbox7[U8a(z[1])]
^ cast_sbox8[U8c(z[1])] ^ cast_sbox7[U8a(z[0])];
t[1] = x[1] = z[0] ^ cast_sbox5[U8a(x[0])]
^ cast_sbox6[U8c(x[0])] ^ cast_sbox7[U8b(x[0])]
^ cast_sbox8[U8d(x[0])] ^ cast_sbox8[U8c(z[0])];
t[2] = x[2] = z[1] ^ cast_sbox5[U8d(x[1])]
^ cast_sbox6[U8c(x[1])] ^ cast_sbox7[U8b(x[1])]
^ cast_sbox8[U8a(x[1])] ^ cast_sbox5[U8b(z[0])];
t[3] = x[3] = z[3] ^ cast_sbox5[U8c(x[2])]
^ cast_sbox6[U8b(x[2])] ^ cast_sbox7[U8d(x[2])]
^ cast_sbox8[U8a(x[2])] ^ cast_sbox6[U8d(z[0])];
break;
}
switch (i & 12) {
case 0:
case 12:
ctx->keys[i+0] = cast_sbox5[U8a(t[2])] ^ cast_sbox6[U8b(t[2])]
^ cast_sbox7[U8d(t[1])] ^ cast_sbox8[U8c(t[1])];
ctx->keys[i+1] = cast_sbox5[U8c(t[2])] ^ cast_sbox6[U8d(t[2])]
^ cast_sbox7[U8b(t[1])] ^ cast_sbox8[U8a(t[1])];
ctx->keys[i+2] = cast_sbox5[U8a(t[3])] ^ cast_sbox6[U8b(t[3])]
^ cast_sbox7[U8d(t[0])] ^ cast_sbox8[U8c(t[0])];
ctx->keys[i+3] = cast_sbox5[U8c(t[3])] ^ cast_sbox6[U8d(t[3])]
^ cast_sbox7[U8b(t[0])] ^ cast_sbox8[U8a(t[0])];
break;
case 4:
case 8:
ctx->keys[i+0] = cast_sbox5[U8d(t[0])] ^ cast_sbox6[U8c(t[0])]
^ cast_sbox7[U8a(t[3])] ^ cast_sbox8[U8b(t[3])];
ctx->keys[i+1] = cast_sbox5[U8b(t[0])] ^ cast_sbox6[U8a(t[0])]
^ cast_sbox7[U8c(t[3])] ^ cast_sbox8[U8d(t[3])];
ctx->keys[i+2] = cast_sbox5[U8d(t[1])] ^ cast_sbox6[U8c(t[1])]
^ cast_sbox7[U8a(t[2])] ^ cast_sbox8[U8b(t[2])];
ctx->keys[i+3] = cast_sbox5[U8b(t[1])] ^ cast_sbox6[U8a(t[1])]
^ cast_sbox7[U8c(t[2])] ^ cast_sbox8[U8d(t[2])];
break;
}
switch (i & 12) {
case 0:
ctx->keys[i+0] ^= cast_sbox5[U8c(z[0])];
ctx->keys[i+1] ^= cast_sbox6[U8c(z[1])];
ctx->keys[i+2] ^= cast_sbox7[U8b(z[2])];
ctx->keys[i+3] ^= cast_sbox8[U8a(z[3])];
break;
case 4:
ctx->keys[i+0] ^= cast_sbox5[U8a(x[2])];
ctx->keys[i+1] ^= cast_sbox6[U8b(x[3])];
ctx->keys[i+2] ^= cast_sbox7[U8d(x[0])];
ctx->keys[i+3] ^= cast_sbox8[U8d(x[1])];
break;
case 8:
ctx->keys[i+0] ^= cast_sbox5[U8b(z[2])];
ctx->keys[i+1] ^= cast_sbox6[U8a(z[3])];
ctx->keys[i+2] ^= cast_sbox7[U8c(z[0])];
ctx->keys[i+3] ^= cast_sbox8[U8c(z[1])];
break;
case 12:
ctx->keys[i+0] ^= cast_sbox5[U8d(x[0])];
ctx->keys[i+1] ^= cast_sbox6[U8d(x[1])];
ctx->keys[i+2] ^= cast_sbox7[U8a(x[2])];
ctx->keys[i+3] ^= cast_sbox8[U8b(x[3])];
break;
}
if (i >= 16) {
ctx->keys[i+0] &= 31;
ctx->keys[i+1] &= 31;
ctx->keys[i+2] &= 31;
ctx->keys[i+3] &= 31;
}
}
/* Wipe clean */
for (i = 0; i < 4; i++) {
t[i] = x[i] = z[i] = 0;
}
}
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