crypto/cast/c_cfb64.c

   1 /*
   2  * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #include <openssl/cast.h>
  11 #include "cast_lcl.h"
  12
  13 /*
  14  * The input and output encrypted as though 64bit cfb mode is being used.
  15  * The extra state information to record how much of the 64bit block we have
  16  * used is contained in *num;
  17  */
  18
  19 void CAST_cfb64_encrypt(const unsigned char *in, unsigned char *out,
  20                         long length, const CAST_KEY *schedule,
  21                         unsigned char *ivec, int *num, int enc)
  22 {
  23     register CAST_LONG v0, v1, t;
  24     register int n = *num;
  25     register long l = length;
  26     CAST_LONG ti[2];
  27     unsigned char *iv, c, cc;
  28
  29     iv = ivec;
  30     if (enc) {
  31         while (l--) {
  32             if (n == 0) {
  33                 n2l(iv, v0);
  34                 ti[0] = v0;
  35                 n2l(iv, v1);
  36                 ti[1] = v1;
  37                 CAST_encrypt((CAST_LONG *)ti, schedule);
  38                 iv = ivec;
  39                 t = ti[0];
  40                 l2n(t, iv);
  41                 t = ti[1];
  42                 l2n(t, iv);
  43                 iv = ivec;
  44             }
  45             c = *(in++) ^ iv[n];
  46             *(out++) = c;
  47             iv[n] = c;
  48             n = (n + 1) & 0x07;
  49         }
  50     } else {
  51         while (l--) {
  52             if (n == 0) {
  53                 n2l(iv, v0);
  54                 ti[0] = v0;
  55                 n2l(iv, v1);
  56                 ti[1] = v1;
  57                 CAST_encrypt((CAST_LONG *)ti, schedule);
  58                 iv = ivec;
  59                 t = ti[0];
  60                 l2n(t, iv);
  61                 t = ti[1];
  62                 l2n(t, iv);
  63                 iv = ivec;
  64             }
  65             cc = *(in++);
  66             c = iv[n];
  67             iv[n] = cc;
  68             *(out++) = c ^ cc;
  69             n = (n + 1) & 0x07;
  70         }
  71     }
  72     v0 = v1 = ti[0] = ti[1] = t = c = cc = 0;
  73     *num = n;
  74 }