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annotate libtomcrypt/src/pk/dh/dh_generate_key.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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1471
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
Matt Johnston <matt@ucc.asn.au>
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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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
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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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 static int _dh_groupsize_to_keysize(int groupsize)
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15 {
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16 /* The strength estimates from https://tools.ietf.org/html/rfc3526#section-8
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17 * We use "Estimate 2" to get an appropriate private key (exponent) size.
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18 */
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19 if (groupsize <= 0) {
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20 return 0;
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21 }
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22 else if (groupsize <= 192) {
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23 return 30; /* 1536-bit => key size 240-bit */
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24 }
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25 else if (groupsize <= 256) {
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26 return 40; /* 2048-bit => key size 320-bit */
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27 }
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28 else if (groupsize <= 384) {
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29 return 52; /* 3072-bit => key size 416-bit */
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30 }
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31 else if (groupsize <= 512) {
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32 return 60; /* 4096-bit => key size 480-bit */
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33 }
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34 else if (groupsize <= 768) {
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35 return 67; /* 6144-bit => key size 536-bit */
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36 }
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37 else if (groupsize <= 1024) {
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38 return 77; /* 8192-bit => key size 616-bit */
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39 }
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40 else {
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41 return 0;
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42 }
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43 }
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44
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45 int dh_generate_key(prng_state *prng, int wprng, dh_key *key)
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46 {
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47 unsigned char *buf;
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48 unsigned long keysize;
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49 int err, max_iterations = LTC_PK_MAX_RETRIES;
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50
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51 LTC_ARGCHK(key != NULL);
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52 LTC_ARGCHK(ltc_mp.name != NULL);
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53
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54 /* good prng? */
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55 if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
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56 return err;
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57 }
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58
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59 keysize = _dh_groupsize_to_keysize(mp_unsigned_bin_size(key->prime));
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60 if (keysize == 0) {
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61 err = CRYPT_INVALID_KEYSIZE;
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62 goto freemp;
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63 }
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64
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65 /* allocate buffer */
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66 buf = XMALLOC(keysize);
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67 if (buf == NULL) {
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68 err = CRYPT_MEM;
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69 goto freemp;
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70 }
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71
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72 key->type = PK_PRIVATE;
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73 do {
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74 /* make up random buf */
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75 if (prng_descriptor[wprng].read(buf, keysize, prng) != keysize) {
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76 err = CRYPT_ERROR_READPRNG;
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77 goto freebuf;
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78 }
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79 /* load the x value - private key */
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80 if ((err = mp_read_unsigned_bin(key->x, buf, keysize)) != CRYPT_OK) {
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81 goto freebuf;
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82 }
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83 /* compute the y value - public key */
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84 if ((err = mp_exptmod(key->base, key->x, key->prime, key->y)) != CRYPT_OK) {
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85 goto freebuf;
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86 }
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87 err = dh_check_pubkey(key);
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88 } while (err != CRYPT_OK && max_iterations-- > 0);
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89
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90 freebuf:
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91 zeromem(buf, keysize);
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92 XFREE(buf);
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93 freemp:
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94 if (err != CRYPT_OK) dh_free(key);
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95 return err;
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96 }
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97
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98 #endif /* LTC_MDH */
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99
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100 /* ref: $Format:%D$ */
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101 /* git commit: $Format:%H$ */
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102 /* commit time: $Format:%ai$ */