openssl/crypto/des/cfb64enc.c

/*
 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

#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;
}