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amiga-apg
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amiga-apg/cast/cast.c

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/*
* CAST-128 in C
* Written by Steve Reid <sreid@sea-to-sky.net>
* 100% Public Domain - no warranty
* Released 1997.10.11
*/
#include "cast.h"
#include "cast_sboxes.h"
/* Macros to access 8-bit bytes out of a 32-bit word */
#define U8a(x) ( (u8) (x>>24) )
#define U8b(x) ( (u8) ((x>>16)&255) )
#define U8c(x) ( (u8) ((x>>8)&255) )
#define U8d(x) ( (u8) ((x)&255) )
/* 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(key->xkey[i] + r, key->xkey[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(key->xkey[i] ^ r, key->xkey[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(key->xkey[i] - r, key->xkey[i+16]); \
l ^= ((cast_sbox1[U8a(t)] + cast_sbox2[U8b(t)]) ^ \
cast_sbox3[U8c(t)]) - cast_sbox4[U8d(t)];
/***** Encryption Function *****/
void cast_encrypt(cast_key* key, u8* inblock, u8* outblock)
{
u32 t, l, r;
/* Get inblock into l,r */
l = ((u32)inblock[0] << 24) | ((u32)inblock[1] << 16) |
((u32)inblock[2] << 8) | (u32)inblock[3];
r = ((u32)inblock[4] << 24) | ((u32)inblock[5] << 16) |
((u32)inblock[6] << 8) | (u32)inblock[7];
/* 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 (key->rounds > 12) {
F1(l, r, 12);
F2(r, l, 13);
F3(l, r, 14);
F1(r, l, 15);
}
/* Put l,r into outblock */
outblock[0] = U8a(r);
outblock[1] = U8b(r);
outblock[2] = U8c(r);
outblock[3] = U8d(r);
outblock[4] = U8a(l);
outblock[5] = U8b(l);
outblock[6] = U8c(l);
outblock[7] = U8d(l);
/* Wipe clean */
t = l = r = 0;
}
/***** Decryption Function *****/
void cast_decrypt(cast_key* key, u8* inblock, u8* outblock)
{
u32 t, l, r;
/* Get inblock into l,r */
r = ((u32)inblock[0] << 24) | ((u32)inblock[1] << 16) |
((u32)inblock[2] << 8) | (u32)inblock[3];
l = ((u32)inblock[4] << 24) | ((u32)inblock[5] << 16) |
((u32)inblock[6] << 8) | (u32)inblock[7];
/* Do the work */
/* Only do full 16 rounds if key length > 80 bits */
if (key->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 */
outblock[0] = U8a(l);
outblock[1] = U8b(l);
outblock[2] = U8c(l);
outblock[3] = U8d(l);
outblock[4] = U8a(r);
outblock[5] = U8b(r);
outblock[6] = U8c(r);
outblock[7] = U8d(r);
/* Wipe clean */
t = l = r = 0;
}
/***** Key Schedual *****/
void cast_setkey(cast_key* key, u8* rawkey, int keybytes)
{
u32 t[4], z[4], x[4];
int i;
/* Set number of rounds to 12 or 16, depending on key length */
key->rounds = (keybytes <= 10 ? 12 : 16);
/* Copy key to workspace x */
for (i = 0; i < 4; i++) {
x[i] = 0;
if ((i*4+0) < keybytes) x[i] = (u32)rawkey[i*4+0] << 24;
if ((i*4+1) < keybytes) x[i] |= (u32)rawkey[i*4+1] << 16;
if ((i*4+2) < keybytes) x[i] |= (u32)rawkey[i*4+2] << 8;
if ((i*4+3) < keybytes) x[i] |= (u32)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:
key->xkey[i+0] = cast_sbox5[U8a(t[2])] ^ cast_sbox6[U8b(t[2])] ^
cast_sbox7[U8d(t[1])] ^ cast_sbox8[U8c(t[1])];
key->xkey[i+1] = cast_sbox5[U8c(t[2])] ^ cast_sbox6[U8d(t[2])] ^
cast_sbox7[U8b(t[1])] ^ cast_sbox8[U8a(t[1])];
key->xkey[i+2] = cast_sbox5[U8a(t[3])] ^ cast_sbox6[U8b(t[3])] ^
cast_sbox7[U8d(t[0])] ^ cast_sbox8[U8c(t[0])];
key->xkey[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:
key->xkey[i+0] = cast_sbox5[U8d(t[0])] ^ cast_sbox6[U8c(t[0])] ^
cast_sbox7[U8a(t[3])] ^ cast_sbox8[U8b(t[3])];
key->xkey[i+1] = cast_sbox5[U8b(t[0])] ^ cast_sbox6[U8a(t[0])] ^
cast_sbox7[U8c(t[3])] ^ cast_sbox8[U8d(t[3])];
key->xkey[i+2] = cast_sbox5[U8d(t[1])] ^ cast_sbox6[U8c(t[1])] ^
cast_sbox7[U8a(t[2])] ^ cast_sbox8[U8b(t[2])];
key->xkey[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:
key->xkey[i+0] ^= cast_sbox5[U8c(z[0])];
key->xkey[i+1] ^= cast_sbox6[U8c(z[1])];
key->xkey[i+2] ^= cast_sbox7[U8b(z[2])];
key->xkey[i+3] ^= cast_sbox8[U8a(z[3])];
break;
case 4:
key->xkey[i+0] ^= cast_sbox5[U8a(x[2])];
key->xkey[i+1] ^= cast_sbox6[U8b(x[3])];
key->xkey[i+2] ^= cast_sbox7[U8d(x[0])];
key->xkey[i+3] ^= cast_sbox8[U8d(x[1])];
break;
case 8:
key->xkey[i+0] ^= cast_sbox5[U8b(z[2])];
key->xkey[i+1] ^= cast_sbox6[U8a(z[3])];
key->xkey[i+2] ^= cast_sbox7[U8c(z[0])];
key->xkey[i+3] ^= cast_sbox8[U8c(z[1])];
break;
case 12:
key->xkey[i+0] ^= cast_sbox5[U8d(x[0])];
key->xkey[i+1] ^= cast_sbox6[U8d(x[1])];
key->xkey[i+2] ^= cast_sbox7[U8a(x[2])];
key->xkey[i+3] ^= cast_sbox8[U8b(x[3])];
break;
}
if (i >= 16) {
key->xkey[i+0] &= 31;
key->xkey[i+1] &= 31;
key->xkey[i+2] &= 31;
key->xkey[i+3] &= 31;
}
}
/* Wipe clean */
for (i = 0; i < 4; i++) {
t[i] = x[i] = z[i] = 0;
}
}
/* Made in Canada */
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