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comparison hmac_init.c @ 0:d7da3b1e1540 libtomcrypt

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put back the 0.95 makefile which was inadvertently merged over
author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:21:40 +0000
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children 5d99163f7e32
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-1:000000000000 0:d7da3b1e1540
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 /* Submited by Dobes Vandermeer ([email protected]) */
12
13 #include "mycrypt.h"
14
15 /*
16 (1) append zeros to the end of K to create a B byte string
17 (e.g., if K is of length 20 bytes and B=64, then K will be
18 appended with 44 zero bytes 0x00)
19 (2) XOR (bitwise exclusive-OR) the B byte string computed in step
20 (1) with ipad (ipad = the byte 0x36 repeated B times)
21 (3) append the stream of data 'text' to the B byte string resulting
22 from step (2)
23 (4) apply H to the stream generated in step (3)
24 (5) XOR (bitwise exclusive-OR) the B byte string computed in
25 step (1) with opad (opad = the byte 0x5C repeated B times.)
26 (6) append the H result from step (4) to the B byte string
27 resulting from step (5)
28 (7) apply H to the stream generated in step (6) and output
29 the result
30 */
31
32 #ifdef HMAC
33
34 #define HMAC_BLOCKSIZE hash_descriptor[hash].blocksize
35
36 int hmac_init(hmac_state *hmac, int hash, const unsigned char *key, unsigned long keylen)
37 {
38 unsigned char buf[MAXBLOCKSIZE];
39 unsigned long hashsize;
40 unsigned long i, z;
41 int err;
42
43 _ARGCHK(hmac != NULL);
44 _ARGCHK(key != NULL);
45
46 if ((err = hash_is_valid(hash)) != CRYPT_OK) {
47 return err;
48 }
49
50 /* valid key length? */
51 if (keylen == 0) {
52 return CRYPT_INVALID_KEYSIZE;
53 }
54
55 hmac->hash = hash;
56
57 // (1) make sure we have a large enough key
58 hashsize = hash_descriptor[hash].hashsize;
59 if(keylen > HMAC_BLOCKSIZE) {
60 z = (unsigned long)sizeof(hmac->key);
61 if ((err = hash_memory(hash, key, keylen, hmac->key, &z)) != CRYPT_OK) {
62 return err;
63 }
64 if(hashsize < HMAC_BLOCKSIZE) {
65 zeromem((hmac->key) + hashsize, (size_t)(HMAC_BLOCKSIZE - hashsize));
66 }
67 keylen = hashsize;
68 } else {
69 memcpy(hmac->key, key, (size_t)keylen);
70 if(keylen < HMAC_BLOCKSIZE) {
71 zeromem((hmac->key) + keylen, (size_t)(HMAC_BLOCKSIZE - keylen));
72 }
73 }
74
75 // Create the initial vector for step (3)
76 for(i=0; i < HMAC_BLOCKSIZE; i++) {
77 buf[i] = hmac->key[i] ^ 0x36;
78 }
79
80 // Pre-pend that to the hash data
81 hash_descriptor[hash].init(&hmac->md);
82 hash_descriptor[hash].process(&hmac->md, buf, HMAC_BLOCKSIZE);
83
84 return CRYPT_OK;
85 }
86
87 #endif