openssl/crypto/rc4/rc4_enc.c

/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#include <openssl/rc4.h>
#include "rc4_locl.h"

/*-
 * RC4 as implemented from a posting from
 * Newsgroups: sci.crypt
 * From: sterndark@netcom.com (David Sterndark)
 * Subject: RC4 Algorithm revealed.
 * Message-ID: <sternCvKL4B.Hyy@netcom.com>
 * Date: Wed, 14 Sep 1994 06:35:31 GMT
 */

void RC4(RC4_KEY *key, size_t len, const unsigned char *indata,
         unsigned char *outdata)
{
    register RC4_INT *d;
    register RC4_INT x, y, tx, ty;
    size_t i;

    x = key->x;
    y = key->y;
    d = key->data;

#define LOOP(in,out) \
                x=((x+1)&0xff); \
                tx=d[x]; \
                y=(tx+y)&0xff; \
                d[x]=ty=d[y]; \
                d[y]=tx; \
                (out) = d[(tx+ty)&0xff]^ (in);

    i = len >> 3;
    if (i) {
        for (;;) {
            LOOP(indata[0], outdata[0]);
            LOOP(indata[1], outdata[1]);
            LOOP(indata[2], outdata[2]);
            LOOP(indata[3], outdata[3]);
            LOOP(indata[4], outdata[4]);
            LOOP(indata[5], outdata[5]);
            LOOP(indata[6], outdata[6]);
            LOOP(indata[7], outdata[7]);
            indata += 8;
            outdata += 8;
            if (--i == 0)
                break;
        }
    }
    i = len & 0x07;
    if (i) {
        for (;;) {
            LOOP(indata[0], outdata[0]);
            if (--i == 0)
                break;
            LOOP(indata[1], outdata[1]);
            if (--i == 0)
                break;
            LOOP(indata[2], outdata[2]);
            if (--i == 0)
                break;
            LOOP(indata[3], outdata[3]);
            if (--i == 0)
                break;
            LOOP(indata[4], outdata[4]);
            if (--i == 0)
                break;
            LOOP(indata[5], outdata[5]);
            if (--i == 0)
                break;
            LOOP(indata[6], outdata[6]);
            if (--i == 0)
                break;
        }
    }
    key->x = x;
    key->y = y;
}