generate_q.c

/*
 * generate_q - Generates the permutations q0 and q1 for twofish.
 * Copyright (C) 1999 Ruud de Rooij <ruud@debian.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <stdio.h>

typedef unsigned char byte;

#define ror4(x) (((x) >> 1) | (((x) & 1) << 3))

static byte q0(byte x)
{

    static byte t0[16] = { 0x8, 0x1, 0x7, 0xD, 0x6, 0xF, 0x3, 0x2,
                           0x0, 0xB, 0x5, 0x9, 0xE, 0xC, 0xA, 0x4 };
    static byte t1[16] = { 0xE, 0xC, 0xB, 0x8, 0x1, 0x2, 0x3, 0x5,
                           0xF, 0x4, 0xA, 0x6, 0x7, 0x0, 0x9, 0xD };
    static byte t2[16] = { 0xB, 0xA, 0x5, 0xE, 0x6, 0xD, 0x9, 0x0,
                           0xC, 0x8, 0xF, 0x3, 0x2, 0x4, 0x7, 0x1 };
    static byte t3[16] = { 0xD, 0x7, 0xF, 0x4, 0x1, 0x2, 0x6, 0xE,
                           0x9, 0xB, 0x3, 0x0, 0x8, 0x5, 0xC, 0xA };

    byte a0 = x / 16;
    byte b0 = x % 16;

    byte a1 = a0 ^ b0;
    byte b1 = a0 ^ ror4(b0) ^ ((8*a0) % 16);

    byte a2 = t0[a1];
    byte b2 = t1[b1];

    byte a3 = a2 ^ b2;
    byte b3 = a2 ^ ror4(b2) ^ ((8*a2) % 16);

    byte a4 = t2[a3];
    byte b4 = t3[b3];

    byte y = 16*b4 + a4;

    return y;
}

static byte q1(byte x)
{
    static byte t0[16] = { 0x2, 0x8, 0xB, 0xD, 0xF, 0x7, 0x6, 0xE,
                           0x3, 0x1, 0x9, 0x4, 0x0, 0xA, 0xC, 0x5 };
    static byte t1[16] = { 0x1, 0xE, 0x2, 0xB, 0x4, 0xC, 0x3, 0x7,
                           0x6, 0xD, 0xA, 0x5, 0xF, 0x9, 0x0, 0x8 };
    static byte t2[16] = { 0x4, 0xC, 0x7, 0x5, 0x1, 0x6, 0x9, 0xA,
                           0x0, 0xE, 0xD, 0x8, 0x2, 0xB, 0x3, 0xF };
    static byte t3[16] = { 0xB, 0x9, 0x5, 0x1, 0xC, 0x3, 0xD, 0xE,
                           0x6, 0x4, 0x7, 0xF, 0x2, 0x0, 0x8, 0xA };

    byte a0 = x / 16;
    byte b0 = x % 16;

    byte a1 = a0 ^ b0;
    byte b1 = a0 ^ ror4(b0) ^ ((8*a0) % 16);

    byte a2 = t0[a1];
    byte b2 = t1[b1];

    byte a3 = a2 ^ b2;
    byte b3 = a2 ^ ror4(b2) ^ ((8*a2) % 16);

    byte a4 = t2[a3];
    byte b4 = t3[b3];

    byte y = 16*b4 + a4;

    return y;
}

int
main(void)
{
    int i, j;

    printf("static byte q0[] = { ");
    for (i = 0; i < 32; i++) {
        for (j = 0; j < 8; j++)
            printf("0x%02X, ", q0(i*8+j));
        if (i == 31)
            printf("};\n\n");
        else
            printf("\n                     ");
    }

    printf("static byte q1[] = { ");
    for (i = 0; i < 32; i++) {
        for (j = 0; j < 8; j++)
            printf("0x%02X, ", q1(i*8+j));
        if (i == 31)
            printf("};\n");
        else
            printf("\n                     ");
    }

    return 0;
}