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comparison ctr_encrypt.c @ 3:7faae8f46238 libtomcrypt-orig

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Branch renaming
author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:25:41 +0000
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-1:000000000000 3:7faae8f46238
1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 *
9 * Tom St Denis, [email protected], http://libtomcrypt.org
10 */
11 #include "mycrypt.h"
12
13 #ifdef CTR
14
15 int ctr_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CTR *ctr)
16 {
17 int x, err;
18
19 _ARGCHK(pt != NULL);
20 _ARGCHK(ct != NULL);
21 _ARGCHK(ctr != NULL);
22
23 if ((err = cipher_is_valid(ctr->cipher)) != CRYPT_OK) {
24 return err;
25 }
26
27 /* is blocklen/padlen valid? */
28 if (ctr->blocklen < 0 || ctr->blocklen > (int)sizeof(ctr->ctr) ||
29 ctr->padlen < 0 || ctr->padlen > (int)sizeof(ctr->pad)) {
30 return CRYPT_INVALID_ARG;
31 }
32
33 while (len-- > 0) {
34 /* is the pad empty? */
35 if (ctr->padlen == ctr->blocklen) {
36 /* increment counter */
37 if (ctr->mode == 0) {
38 /* little-endian */
39 for (x = 0; x < ctr->blocklen; x++) {
40 ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
41 if (ctr->ctr[x] != (unsigned char)0) {
42 break;
43 }
44 }
45 } else {
46 /* big-endian */
47 for (x = ctr->blocklen-1; x >= 0; x--) {
48 ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
49 if (ctr->ctr[x] != (unsigned char)0) {
50 break;
51 }
52 }
53 }
54
55 /* encrypt it */
56 cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key);
57 ctr->padlen = 0;
58 }
59 *ct++ = *pt++ ^ ctr->pad[ctr->padlen++];
60 }
61 return CRYPT_OK;
62 }
63
64 #endif