cfb64enc.c

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/* crypto/des/cfb64enc.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 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;
    }