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comparison libtomcrypt/src/encauth/ocb3/ocb3_done.c @ 1471:6dba84798cd5

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Update to libtomcrypt 1.18.1, merged with Dropbear changes
author Matt Johnston <matt@ucc.asn.au>
date Fri, 09 Feb 2018 21:44:05 +0800
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1470:8bba51a55704 1471:6dba84798cd5
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
10 /**
11 @file ocb3_done.c
12 OCB implementation, INTERNAL ONLY helper, by Tom St Denis
13 */
14 #include "tomcrypt.h"
15
16 #ifdef LTC_OCB3_MODE
17
18 /**
19 Finish OCB processing and compute the tag
20 @param ocb The OCB state
21 @param tag [out] The destination for the authentication tag
22 @param taglen [in/out] The max size and resulting size of the authentication tag
23 @return CRYPT_OK if successful
24 */
25 int ocb3_done(ocb3_state *ocb, unsigned char *tag, unsigned long *taglen)
26 {
27 unsigned char tmp[MAXBLOCKSIZE];
28 int err, x;
29
30 LTC_ARGCHK(ocb != NULL);
31 LTC_ARGCHK(tag != NULL);
32 LTC_ARGCHK(taglen != NULL);
33 if ((err = cipher_is_valid(ocb->cipher)) != CRYPT_OK) {
34 goto LBL_ERR;
35 }
36
37 /* check taglen */
38 if ((int)*taglen < ocb->tag_len) {
39 *taglen = (unsigned long)ocb->tag_len;
40 return CRYPT_BUFFER_OVERFLOW;
41 }
42
43 /* finalize AAD processing */
44
45 if (ocb->adata_buffer_bytes>0) {
46 /* Offset_* = Offset_m xor L_* */
47 ocb3_int_xor_blocks(ocb->aOffset_current, ocb->aOffset_current, ocb->L_star, ocb->block_len);
48
49 /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
50 ocb3_int_xor_blocks(tmp, ocb->adata_buffer, ocb->aOffset_current, ocb->adata_buffer_bytes);
51 for(x=ocb->adata_buffer_bytes; x<ocb->block_len; x++) {
52 if (x == ocb->adata_buffer_bytes) {
53 tmp[x] = 0x80 ^ ocb->aOffset_current[x];
54 }
55 else {
56 tmp[x] = 0x00 ^ ocb->aOffset_current[x];
57 }
58 }
59
60 /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
61 if ((err = cipher_descriptor[ocb->cipher].ecb_encrypt(tmp, tmp, &ocb->key)) != CRYPT_OK) {
62 goto LBL_ERR;
63 }
64 ocb3_int_xor_blocks(ocb->aSum_current, ocb->aSum_current, tmp, ocb->block_len);
65 }
66
67 /* finalize TAG computing */
68
69 /* at this point ocb->aSum_current = HASH(K, A) */
70 /* tag = tag ^ HASH(K, A) */
71 ocb3_int_xor_blocks(tmp, ocb->tag_part, ocb->aSum_current, ocb->block_len);
72
73 /* copy tag bytes */
74 for(x = 0; x < ocb->tag_len; x++) tag[x] = tmp[x];
75 *taglen = (unsigned long)ocb->tag_len;
76
77 err = CRYPT_OK;
78
79 LBL_ERR:
80 #ifdef LTC_CLEAN_STACK
81 zeromem(tmp, MAXBLOCKSIZE);
82 zeromem(ocb, sizeof(*ocb));
83 #endif
84
85 return err;
86 }
87
88 #endif
89
90 /* ref: $Format:%D$ */
91 /* git commit: $Format:%H$ */
92 /* commit time: $Format:%ai$ */