crypto/des/cfb64enc.c

/* crypto/des/cfb64enc.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 "des_locl.h"

/*
 * The input and output encrypted as though 64bit cfb mode is being used.
 * The extra state information to record how much of the 64bit block we have
 * used is contained in *num;
 */

void DES_cfb64_encrypt(const unsigned char *in, unsigned char *out,
                       long length, DES_key_schedule *schedule,
                       DES_cblock *ivec, int *num, int enc)
{
    register DES_LONG v0, v1;
    register long l = length;
    register int n = *num;
    DES_LONG ti[2];
    unsigned char *iv, c, cc;

    iv = &(*ivec)[0];
    if (enc) {
        while (l--) {
            if (n == 0) {
                c2l(iv, v0);
                ti[0] = v0;
                c2l(iv, v1);
                ti[1] = v1;
                DES_encrypt1(ti, schedule, DES_ENCRYPT);
                iv = &(*ivec)[0];
                v0 = ti[0];
                l2c(v0, iv);
                v0 = ti[1];
                l2c(v0, iv);
                iv = &(*ivec)[0];
            }
            c = *(in++) ^ iv[n];
            *(out++) = c;
            iv[n] = c;
            n = (n + 1) & 0x07;
        }
    } else {
        while (l--) {
            if (n == 0) {
                c2l(iv, v0);
                ti[0] = v0;
                c2l(iv, v1);
                ti[1] = v1;
                DES_encrypt1(ti, schedule, DES_ENCRYPT);
                iv = &(*ivec)[0];
                v0 = ti[0];
                l2c(v0, iv);
                v0 = ti[1];
                l2c(v0, iv);
                iv = &(*ivec)[0];
            }
            cc = *(in++);
            c = iv[n];
            iv[n] = cc;
            *(out++) = c ^ cc;
            n = (n + 1) & 0x07;
        }
    }
    v0 = v1 = ti[0] = ti[1] = c = cc = 0;
    *num = n;
}