ofb_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 "des_locl.h"

/*
 * The input and output are loaded in multiples of 8 bits. What this means is
 * that if you hame numbits=12 and length=2 the first 12 bits will be
 * retrieved from the first byte and half the second.  The second 12 bits
 * will come from the 3rd and half the 4th byte.
 */
void DES_ofb_encrypt(const unsigned char *in, unsigned char *out, int numbits,
                     long length, DES_key_schedule *schedule,
                     DES_cblock *ivec)
{
    register DES_LONG d0, d1, vv0, vv1, v0, v1, n = (numbits + 7) / 8;
    register DES_LONG mask0, mask1;
    register long l = length;
    register int num = numbits;
    DES_LONG ti[2];
    unsigned char *iv;

    if (num > 64)
        return;
    if (num > 32) {
        mask0 = 0xffffffffL;
        if (num >= 64)
            mask1 = mask0;
        else
            mask1 = (1L << (num - 32)) - 1;
    } else {
        if (num == 32)
            mask0 = 0xffffffffL;
        else
            mask0 = (1L << num) - 1;
        mask1 = 0x00000000L;
    }

    iv = &(*ivec)[0];
    c2l(iv, v0);
    c2l(iv, v1);
    ti[0] = v0;
    ti[1] = v1;
    while (l-- > 0) {
        ti[0] = v0;
        ti[1] = v1;
        DES_encrypt1((DES_LONG *)ti, schedule, DES_ENCRYPT);
        vv0 = ti[0];
        vv1 = ti[1];
        c2ln(in, d0, d1, n);
        in += n;
        d0 = (d0 ^ vv0) & mask0;
        d1 = (d1 ^ vv1) & mask1;
        l2cn(d0, d1, out, n);
        out += n;

        if (num == 32) {
            v0 = v1;
            v1 = vv0;
        } else if (num == 64) {
            v0 = vv0;
            v1 = vv1;
        } else if (num > 32) {  /* && num != 64 */
            v0 = ((v1 >> (num - 32)) | (vv0 << (64 - num))) & 0xffffffffL;
            v1 = ((vv0 >> (num - 32)) | (vv1 << (64 - num))) & 0xffffffffL;
        } else {                /* num < 32 */

            v0 = ((v0 >> num) | (v1 << (32 - num))) & 0xffffffffL;
            v1 = ((v1 >> num) | (vv0 << (32 - num))) & 0xffffffffL;
        }
    }
    iv = &(*ivec)[0];
    l2c(v0, iv);
    l2c(v1, iv);
    v0 = v1 = d0 = d1 = ti[0] = ti[1] = vv0 = vv1 = 0;
}