ofb_enc.c revision 296465 
1/* crypto/des/ofb_enc.c */
2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to.  The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 *    notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 *    notice, this list of conditions and the following disclaimer in the
30 *    documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 *    must display the following acknowledgement:
33 *    "This product includes cryptographic software written by
34 *     Eric Young (eay@cryptsoft.com)"
35 *    The word 'cryptographic' can be left out if the rouines from the library
36 *    being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 *    the apps directory (application code) you must include an acknowledgement:
39 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed.  i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58
59#include "des_locl.h"
60
61/*
62 * The input and output are loaded in multiples of 8 bits. What this means is
63 * that if you hame numbits=12 and length=2 the first 12 bits will be
64 * retrieved from the first byte and half the second.  The second 12 bits
65 * will come from the 3rd and half the 4th byte.
66 */
67void DES_ofb_encrypt(const unsigned char *in, unsigned char *out, int numbits,
68                     long length, DES_key_schedule *schedule,
69                     DES_cblock *ivec)
70{
71    register DES_LONG d0, d1, vv0, vv1, v0, v1, n = (numbits + 7) / 8;
72    register DES_LONG mask0, mask1;
73    register long l = length;
74    register int num = numbits;
75    DES_LONG ti[2];
76    unsigned char *iv;
77
78    if (num > 64)
79        return;
80    if (num > 32) {
81        mask0 = 0xffffffffL;
82        if (num >= 64)
83            mask1 = mask0;
84        else
85            mask1 = (1L << (num - 32)) - 1;
86    } else {
87        if (num == 32)
88            mask0 = 0xffffffffL;
89        else
90            mask0 = (1L << num) - 1;
91        mask1 = 0x00000000L;
92    }
93
94    iv = &(*ivec)[0];
95    c2l(iv, v0);
96    c2l(iv, v1);
97    ti[0] = v0;
98    ti[1] = v1;
99    while (l-- > 0) {
100        ti[0] = v0;
101        ti[1] = v1;
102        DES_encrypt1((DES_LONG *)ti, schedule, DES_ENCRYPT);
103        vv0 = ti[0];
104        vv1 = ti[1];
105        c2ln(in, d0, d1, n);
106        in += n;
107        d0 = (d0 ^ vv0) & mask0;
108        d1 = (d1 ^ vv1) & mask1;
109        l2cn(d0, d1, out, n);
110        out += n;
111
112        if (num == 32) {
113            v0 = v1;
114            v1 = vv0;
115        } else if (num == 64) {
116            v0 = vv0;
117            v1 = vv1;
118        } else if (num > 32) {  /* && num != 64 */
119            v0 = ((v1 >> (num - 32)) | (vv0 << (64 - num))) & 0xffffffffL;
120            v1 = ((vv0 >> (num - 32)) | (vv1 << (64 - num))) & 0xffffffffL;
121        } else {                /* num < 32 */
122
123            v0 = ((v0 >> num) | (v1 << (32 - num))) & 0xffffffffL;
124            v1 = ((v1 >> num) | (vv0 << (32 - num))) & 0xffffffffL;
125        }
126    }
127    iv = &(*ivec)[0];
128    l2c(v0, iv);
129    l2c(v1, iv);
130    v0 = v1 = d0 = d1 = ti[0] = ti[1] = vv0 = vv1 = 0;
131}
132