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, tomstdenis@gmail.com, http://libtomcrypt.com
10 */
11 #include "tomcrypt.h"
12
13 /**
14 @file xcbc_done.c
15 XCBC Support, terminate the state
16 */
17
18 #ifdef LTC_XCBC
19
20 /** Terminate the XCBC-MAC state
21 @param xcbc XCBC state to terminate
22 @param out [out] Destination for the MAC tag
23 @param outlen [in/out] Destination size and final tag size
24 Return CRYPT_OK on success
25 */
xcbc_done(xcbc_state * xcbc,unsigned char * out,unsigned long * outlen)26 int xcbc_done(xcbc_state *xcbc, unsigned char *out, unsigned long *outlen)
27 {
28 int err, x;
29 LTC_ARGCHK(xcbc != NULL);
30 LTC_ARGCHK(out != NULL);
31
32 /* check structure */
33 if ((err = cipher_is_valid(xcbc->cipher)) != CRYPT_OK) {
34 return err;
35 }
36
37 if ((xcbc->blocksize > cipher_descriptor[xcbc->cipher].block_length) || (xcbc->blocksize < 0) ||
38 (xcbc->buflen > xcbc->blocksize) || (xcbc->buflen < 0)) {
39 return CRYPT_INVALID_ARG;
40 }
41
42 /* which key do we use? */
43 if (xcbc->buflen == xcbc->blocksize) {
44 /* k2 */
45 for (x = 0; x < xcbc->blocksize; x++) {
46 xcbc->IV[x] ^= xcbc->K[1][x];
47 }
48 } else {
49 xcbc->IV[xcbc->buflen] ^= 0x80;
50 /* k3 */
51 for (x = 0; x < xcbc->blocksize; x++) {
52 xcbc->IV[x] ^= xcbc->K[2][x];
53 }
54 }
55
56 /* encrypt */
57 cipher_descriptor[xcbc->cipher].ecb_encrypt(xcbc->IV, xcbc->IV, &xcbc->key);
58 cipher_descriptor[xcbc->cipher].done(&xcbc->key);
59
60 /* extract tag */
61 for (x = 0; x < xcbc->blocksize && (unsigned long)x < *outlen; x++) {
62 out[x] = xcbc->IV[x];
63 }
64 *outlen = x;
65
66 #ifdef LTC_CLEAN_STACK
67 zeromem(xcbc, sizeof(*xcbc));
68 #endif
69 return CRYPT_OK;
70 }
71
72 #endif
73
74 /* $Source: /cvs/libtom/libtomcrypt/src/mac/xcbc/xcbc_done.c,v $ */
75 /* $Revision: 1.4 $ */
76 /* $Date: 2006/11/07 03:23:46 $ */
77
78