rc2.c 7.55 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
/*
 * dlls/rsaen/rc2.c
 * RC2 functions  
 *
 * Copyright 2004 Michael Jung
 * Based on public domain code by Tom St Denis (tomstdenis@iahu.ca)
 *
 * This 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.
 *
 * This 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 this library; if not, write to the Free Software
20
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203
 */

/*
 * This file contains code from the LibTomCrypt cryptographic 
 * library written by Tom St Denis (tomstdenis@iahu.ca). LibTomCrypt
 * is in the public domain. The code in this file is tailored to
 * special requirements. Take a look at http://libtomcrypt.org for the
 * original version. 
 */

#include "tomcrypt.h"

/* 256-entry permutation table, probably derived somehow from pi */
static const unsigned char permute[256] = {
        217,120,249,196, 25,221,181,237, 40,233,253,121, 74,160,216,157,
        198,126, 55,131, 43,118, 83,142, 98, 76,100,136, 68,139,251,162,
         23,154, 89,245,135,179, 79, 19, 97, 69,109,141,  9,129,125, 50,
        189,143, 64,235,134,183,123, 11,240,149, 33, 34, 92,107, 78,130,
         84,214,101,147,206, 96,178, 28,115, 86,192, 20,167,140,241,220,
         18,117,202, 31, 59,190,228,209, 66, 61,212, 48,163, 60,182, 38,
        111,191, 14,218, 70,105,  7, 87, 39,242, 29,155,188,148, 67,  3,
        248, 17,199,246,144,239, 62,231,  6,195,213, 47,200,102, 30,215,
          8,232,234,222,128, 82,238,247,132,170,114,172, 53, 77,106, 42,
        150, 26,210,113, 90, 21, 73,116, 75,159,208, 94,  4, 24,164,236,
        194,224, 65,110, 15, 81,203,204, 36,145,175, 80,161,244,112, 57,
        153,124, 58,133, 35,184,180,122,252,  2, 54, 91, 37, 85,151, 49,
         45, 93,250,152,227,138,146,174,  5,223, 41, 16,103,108,186,201,
        211,  0,230,207,225,158,168, 44, 99, 22,  1, 63, 88,226,137,169,
         13, 56, 52, 27,171, 51,255,176,187, 72, 12, 95,185,177,205, 46,
        197,243,219, 71,229,165,156,119, 10,166, 32,104,254,127,193,173
};

int rc2_setup(const unsigned char *key, int keylen, int bits, int rounds, rc2_key *rc2)
{
   unsigned *xkey = rc2->xkey;
   unsigned char tmp[128];
   unsigned T8, TM;
   int i;

   if (keylen < 5 || keylen > 128) {
      return CRYPT_INVALID_KEYSIZE;
   }

   if (rounds != 0 && rounds != 16) {
      return CRYPT_INVALID_ROUNDS;
   }

    /* Following comment is from Eric Young's rc2 code: */
    /* It has come to my attention that there are 2 versions of the RC2
     * key schedule.  One which is normal, and anther which has a hook to
     * use a reduced key length.
     * BSAFE uses the 'retarded' version.  What I previously shipped is
     * the same as specifying 1024 for the 'bits' parameter.  Bsafe uses
     * a version where the bits parameter is the same as len*8 */
    /* Seems like MS uses the 'retarded' version, too.
     * Adjust effective keylen bits */
   if (bits <= 0) bits = keylen << 3;
   if (bits > 1024) bits = 1024;
   
   for (i = 0; i < keylen; i++) {
       tmp[i] = key[i] & 255;
   }

    /* Phase 1: Expand input key to 128 bytes */
    if (keylen < 128) {
        for (i = keylen; i < 128; i++) {
            tmp[i] = permute[(tmp[i - 1] + tmp[i - keylen]) & 255];
        }
    }
    
    /* Phase 2 - reduce effective key size to "bits" */
    /*bits = keylen<<3; */
    T8   = (unsigned)(bits+7)>>3;
    TM   = (255 >> (unsigned)(7 & -bits));
    tmp[128 - T8] = permute[tmp[128 - T8] & TM];
    for (i = 127 - T8; i >= 0; i--) {
        tmp[i] = permute[tmp[i + 1] ^ tmp[i + T8]];
    }

    /* Phase 3 - copy to xkey in little-endian order */
    for (i = 0; i < 64; i++) {
        xkey[i] =  (unsigned)tmp[2*i] + ((unsigned)tmp[2*i+1] << 8);
    }        

    return CRYPT_OK;
}

/**********************************************************************\
* Encrypt an 8-byte block of plaintext using the given key.            *
\**********************************************************************/
void rc2_ecb_encrypt( const unsigned char *plain,
                            unsigned char *cipher,
                            rc2_key *rc2)
{
    unsigned *xkey;
    unsigned x76, x54, x32, x10, i;

    xkey = rc2->xkey;

    x76 = ((unsigned)plain[7] << 8) + (unsigned)plain[6];
    x54 = ((unsigned)plain[5] << 8) + (unsigned)plain[4];
    x32 = ((unsigned)plain[3] << 8) + (unsigned)plain[2];
    x10 = ((unsigned)plain[1] << 8) + (unsigned)plain[0];

    for (i = 0; i < 16; i++) {
        x10 = (x10 + (x32 & ~x76) + (x54 & x76) + xkey[4*i+0]) & 0xFFFF;
        x10 = ((x10 << 1) | (x10 >> 15));

        x32 = (x32 + (x54 & ~x10) + (x76 & x10) + xkey[4*i+1]) & 0xFFFF;
        x32 = ((x32 << 2) | (x32 >> 14));

        x54 = (x54 + (x76 & ~x32) + (x10 & x32) + xkey[4*i+2]) & 0xFFFF;
        x54 = ((x54 << 3) | (x54 >> 13));

        x76 = (x76 + (x10 & ~x54) + (x32 & x54) + xkey[4*i+3]) & 0xFFFF;
        x76 = ((x76 << 5) | (x76 >> 11));

        if (i == 4 || i == 10) {
            x10 = (x10 + xkey[x76 & 63]) & 0xFFFF;
            x32 = (x32 + xkey[x10 & 63]) & 0xFFFF;
            x54 = (x54 + xkey[x32 & 63]) & 0xFFFF;
            x76 = (x76 + xkey[x54 & 63]) & 0xFFFF;
        }
    }

    cipher[0] = (unsigned char)x10;
    cipher[1] = (unsigned char)(x10 >> 8);
    cipher[2] = (unsigned char)x32;
    cipher[3] = (unsigned char)(x32 >> 8);
    cipher[4] = (unsigned char)x54;
    cipher[5] = (unsigned char)(x54 >> 8);
    cipher[6] = (unsigned char)x76;
    cipher[7] = (unsigned char)(x76 >> 8);
}

/**********************************************************************\
* Decrypt an 8-byte block of ciphertext using the given key.           *
\**********************************************************************/
void rc2_ecb_decrypt( const unsigned char *cipher,
                            unsigned char *plain,
                            rc2_key *rc2)
{
    unsigned x76, x54, x32, x10;
    unsigned *xkey;
    int i;

    xkey = rc2->xkey;

    x76 = ((unsigned)cipher[7] << 8) + (unsigned)cipher[6];
    x54 = ((unsigned)cipher[5] << 8) + (unsigned)cipher[4];
    x32 = ((unsigned)cipher[3] << 8) + (unsigned)cipher[2];
    x10 = ((unsigned)cipher[1] << 8) + (unsigned)cipher[0];

    for (i = 15; i >= 0; i--) {
        if (i == 4 || i == 10) {
            x76 = (x76 - xkey[x54 & 63]) & 0xFFFF;
            x54 = (x54 - xkey[x32 & 63]) & 0xFFFF;
            x32 = (x32 - xkey[x10 & 63]) & 0xFFFF;
            x10 = (x10 - xkey[x76 & 63]) & 0xFFFF;
        }

        x76 = ((x76 << 11) | (x76 >> 5));
        x76 = (x76 - ((x10 & ~x54) + (x32 & x54) + xkey[4*i+3])) & 0xFFFF;

        x54 = ((x54 << 13) | (x54 >> 3));
        x54 = (x54 - ((x76 & ~x32) + (x10 & x32) + xkey[4*i+2])) & 0xFFFF;

        x32 = ((x32 << 14) | (x32 >> 2));
        x32 = (x32 - ((x54 & ~x10) + (x76 & x10) + xkey[4*i+1])) & 0xFFFF;

        x10 = ((x10 << 15) | (x10 >> 1));
        x10 = (x10 - ((x32 & ~x76) + (x54 & x76) + xkey[4*i+0])) & 0xFFFF;
    }

    plain[0] = (unsigned char)x10;
    plain[1] = (unsigned char)(x10 >> 8);
    plain[2] = (unsigned char)x32;
    plain[3] = (unsigned char)(x32 >> 8);
    plain[4] = (unsigned char)x54;
    plain[5] = (unsigned char)(x54 >> 8);
    plain[6] = (unsigned char)x76;
    plain[7] = (unsigned char)(x76 >> 8);
}