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comparison src/encauth/eax/eax_decrypt_verify_memory.c @ 191:1c15b283127b libtomcrypt-orig

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Import of libtomcrypt 1.02 with manual path rename rearrangement etc
author Matt Johnston <matt@ucc.asn.au>
date Fri, 06 May 2005 13:23:02 +0000
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children 39d5d58461d6
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143:5d99163f7e32 191:1c15b283127b
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
12 /**
13 @file eax_decrypt_verify_memory.c
14 EAX implementation, decrypt block of memory, by Tom St Denis
15 */
16 #include "tomcrypt.h"
17
18 #ifdef EAX_MODE
19
20 /**
21 Decrypt a block of memory and verify the provided MAC tag with EAX
22 @param cipher The index of the cipher desired
23 @param key The secret key
24 @param keylen The length of the key (octets)
25 @param nonce The nonce data (use once) for the session
26 @param noncelen The length of the nonce data.
27 @param header The session header data
28 @param headerlen The length of the header (octets)
29 @param ct The ciphertext
30 @param ctlen The length of the ciphertext (octets)
31 @param pt [out] The plaintext
32 @param tag The authentication tag provided by the encoder
33 @param taglen [in/out] The length of the tag (octets)
34 @param stat [out] The result of the decryption (1==valid tag, 0==invalid)
35 @return CRYPT_OK if successful regardless of the resulting tag comparison
36 */
37 int eax_decrypt_verify_memory(int cipher,
38 const unsigned char *key, unsigned long keylen,
39 const unsigned char *nonce, unsigned long noncelen,
40 const unsigned char *header, unsigned long headerlen,
41 const unsigned char *ct, unsigned long ctlen,
42 unsigned char *pt,
43 unsigned char *tag, unsigned long taglen,
44 int *stat)
45 {
46 int err;
47 eax_state *eax;
48 unsigned char *buf;
49 unsigned long buflen;
50
51 LTC_ARGCHK(stat != NULL);
52 LTC_ARGCHK(key != NULL);
53 LTC_ARGCHK(pt != NULL);
54 LTC_ARGCHK(ct != NULL);
55 LTC_ARGCHK(tag != NULL);
56
57 /* default to zero */
58 *stat = 0;
59
60 /* allocate ram */
61 buf = XMALLOC(taglen);
62 eax = XMALLOC(sizeof(*eax));
63 if (eax == NULL || buf == NULL) {
64 if (eax != NULL) {
65 XFREE(eax);
66 }
67 if (buf != NULL) {
68 XFREE(buf);
69 }
70 return CRYPT_MEM;
71 }
72
73 if ((err = eax_init(eax, cipher, key, keylen, nonce, noncelen, header, headerlen)) != CRYPT_OK) {
74 goto LBL_ERR;
75 }
76
77 if ((err = eax_decrypt(eax, ct, pt, ctlen)) != CRYPT_OK) {
78 goto LBL_ERR;
79 }
80
81 buflen = taglen;
82 if ((err = eax_done(eax, buf, &buflen)) != CRYPT_OK) {
83 goto LBL_ERR;
84 }
85
86 /* compare tags */
87 if (buflen >= taglen && memcmp(buf, tag, taglen) == 0) {
88 *stat = 1;
89 }
90
91 err = CRYPT_OK;
92 LBL_ERR:
93 #ifdef LTC_CLEAN_STACK
94 zeromem(buf, taglen);
95 zeromem(eax, sizeof(*eax));
96 #endif
97
98 XFREE(eax);
99 XFREE(buf);
100
101 return err;
102 }
103
104 #endif