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annotate libtomcrypt/src/pk/dh/dh_check_pubkey.c @ 1520:84578193ef47

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author Matt Johnston <matt@ucc.asn.au>
date Sun, 18 Feb 2018 23:48:32 +0800
parents 6dba84798cd5
children
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1471
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 */
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9
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10 #include "tomcrypt.h"
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11
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12 #ifdef LTC_MDH
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13
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14 /**
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15 Check DH public key (INTERNAL ONLY, not part of public API)
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16 @param key The key you wish to test
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17 @return CRYPT_OK if successful
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18 */
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19 int dh_check_pubkey(dh_key *key)
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20 {
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21 void *p_minus1;
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22 ltc_mp_digit digit;
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23 int i, digit_count, bits_set = 0, err;
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24
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25 LTC_ARGCHK(key != NULL);
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26
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27 if ((err = mp_init(&p_minus1)) != CRYPT_OK) {
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28 return err;
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29 }
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30
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31 /* avoid: y <= 1 OR y >= p-1 */
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32 if ((err = mp_sub_d(key->prime, 1, p_minus1)) != CRYPT_OK) {
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33 goto error;
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34 }
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35 if (mp_cmp(key->y, p_minus1) != LTC_MP_LT || mp_cmp_d(key->y, 1) != LTC_MP_GT) {
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36 err = CRYPT_INVALID_ARG;
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37 goto error;
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38 }
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39
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40 /* public key must have more than one bit set */
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41 digit_count = mp_get_digit_count(key->y);
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42 for (i = 0; i < digit_count && bits_set < 2; i++) {
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43 digit = mp_get_digit(key->y, i);
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44 while (digit > 0) {
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45 if (digit & 1) bits_set++;
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46 digit >>= 1;
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47 }
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48 }
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49 if (bits_set > 1) {
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50 err = CRYPT_OK;
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51 }
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52 else {
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53 err = CRYPT_INVALID_ARG;
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54 }
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55
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56 error:
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57 mp_clear(p_minus1);
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58 return err;
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59 }
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60
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61 #endif /* LTC_MDH */
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62
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63 /* ref: $Format:%D$ */
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64 /* git commit: $Format:%H$ */
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65 /* commit time: $Format:%ai$ */