Return to rc4.c CVS log

Up to [ELWIX - Embedded LightWeight unIX -] / embedaddon / axTLS / crypto

Annotation of embedaddon/axTLS/crypto/rc4.c, revision 1.1

1.1     ! misho       1: /*
        !             2:  * Copyright (c) 2007, Cameron Rich
        !             3:  * 
        !             4:  * All rights reserved.
        !             5:  * 
        !             6:  * Redistribution and use in source and binary forms, with or without 
        !             7:  * modification, are permitted provided that the following conditions are met:
        !             8:  *
        !             9:  * * Redistributions of source code must retain the above copyright notice, 
        !            10:  *   this list of conditions and the following disclaimer.
        !            11:  * * Redistributions in binary form must reproduce the above copyright notice, 
        !            12:  *   this list of conditions and the following disclaimer in the documentation 
        !            13:  *   and/or other materials provided with the distribution.
        !            14:  * * Neither the name of the axTLS project nor the names of its contributors 
        !            15:  *   may be used to endorse or promote products derived from this software 
        !            16:  *   without specific prior written permission.
        !            17:  *
        !            18:  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
        !            19:  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
        !            20:  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
        !            21:  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
        !            22:  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
        !            23:  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
        !            24:  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
        !            25:  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
        !            26:  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
        !            27:  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
        !            28:  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
        !            29:  */
        !            30: 
        !            31: /**
        !            32:  * An implementation of the RC4/ARC4 algorithm.
        !            33:  * Originally written by Christophe Devine.
        !            34:  */
        !            35: 
        !            36: #include <string.h>
        !            37: #include "os_port.h"
        !            38: #include "crypto.h"
        !            39: 
        !            40: /**
        !            41:  * Get ready for an encrypt/decrypt operation
        !            42:  */
        !            43: void RC4_setup(RC4_CTX *ctx, const uint8_t *key, int length)
        !            44: {
        !            45:     int i, j = 0, k = 0, a;
        !            46:     uint8_t *m;
        !            47: 
        !            48:     ctx->x = 0;
        !            49:     ctx->y = 0;
        !            50:     m = ctx->m;
        !            51: 
        !            52:     for (i = 0; i < 256; i++)
        !            53:         m[i] = i;
        !            54: 
        !            55:     for (i = 0; i < 256; i++)
        !            56:     {
        !            57:         a = m[i];
        !            58:         j = (uint8_t)(j + a + key[k]);
        !            59:         m[i] = m[j]; 
        !            60:         m[j] = a;
        !            61: 
        !            62:         if (++k >= length) 
        !            63:             k = 0;
        !            64:     }
        !            65: }
        !            66: 
        !            67: /**
        !            68:  * Perform the encrypt/decrypt operation (can use it for either since
        !            69:  * this is a stream cipher).
        !            70:  * NOTE: *msg and *out must be the same pointer (performance tweak)
        !            71:  */
        !            72: void RC4_crypt(RC4_CTX *ctx, const uint8_t *msg, uint8_t *out, int length)
        !            73: { 
        !            74:     int i;
        !            75:     uint8_t *m, x, y, a, b;
        !            76: 
        !            77:     x = ctx->x;
        !            78:     y = ctx->y;
        !            79:     m = ctx->m;
        !            80: 
        !            81:     for (i = 0; i < length; i++)
        !            82:     {
        !            83:         a = m[++x];
        !            84:         y += a;
        !            85:         m[x] = b = m[y];
        !            86:         m[y] = a;
        !            87:         out[i] ^= m[(uint8_t)(a + b)];
        !            88:     }
        !            89: 
        !            90:     ctx->x = x;
        !            91:     ctx->y = y;
        !            92: }