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comparison libtomcrypt/src/pk/dh/dh_check_pubkey.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 #include "tomcrypt.h"
11
12 #ifdef LTC_MDH
13
14 /**
15 Check DH public key (INTERNAL ONLY, not part of public API)
16 @param key The key you wish to test
17 @return CRYPT_OK if successful
18 */
19 int dh_check_pubkey(dh_key *key)
20 {
21 void *p_minus1;
22 ltc_mp_digit digit;
23 int i, digit_count, bits_set = 0, err;
24
25 LTC_ARGCHK(key != NULL);
26
27 if ((err = mp_init(&p_minus1)) != CRYPT_OK) {
28 return err;
29 }
30
31 /* avoid: y <= 1 OR y >= p-1 */
32 if ((err = mp_sub_d(key->prime, 1, p_minus1)) != CRYPT_OK) {
33 goto error;
34 }
35 if (mp_cmp(key->y, p_minus1) != LTC_MP_LT || mp_cmp_d(key->y, 1) != LTC_MP_GT) {
36 err = CRYPT_INVALID_ARG;
37 goto error;
38 }
39
40 /* public key must have more than one bit set */
41 digit_count = mp_get_digit_count(key->y);
42 for (i = 0; i < digit_count && bits_set < 2; i++) {
43 digit = mp_get_digit(key->y, i);
44 while (digit > 0) {
45 if (digit & 1) bits_set++;
46 digit >>= 1;
47 }
48 }
49 if (bits_set > 1) {
50 err = CRYPT_OK;
51 }
52 else {
53 err = CRYPT_INVALID_ARG;
54 }
55
56 error:
57 mp_clear(p_minus1);
58 return err;
59 }
60
61 #endif /* LTC_MDH */
62
63 /* ref: $Format:%D$ */
64 /* git commit: $Format:%H$ */
65 /* commit time: $Format:%ai$ */