ofb_enc.c

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/* crypto/des/ofb_enc.c */
/* Copyright (C) 1995-1998 Eric Young ([email protected])
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young ([email protected]).
 * 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 ([email protected]).
 * 
 * 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 ([email protected])"
 *    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 ([email protected])"
 * 
 * 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;
    }