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103 lines
2.6 KiB
C
103 lines
2.6 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*/
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#include "tomcrypt.h"
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#ifdef LTC_MDH
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static int _dh_groupsize_to_keysize(int groupsize)
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{
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/* The strength estimates from https://tools.ietf.org/html/rfc3526#section-8
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* We use "Estimate 2" to get an appropriate private key (exponent) size.
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*/
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if (groupsize <= 0) {
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return 0;
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}
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else if (groupsize <= 192) {
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return 30; /* 1536-bit => key size 240-bit */
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}
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else if (groupsize <= 256) {
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return 40; /* 2048-bit => key size 320-bit */
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}
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else if (groupsize <= 384) {
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return 52; /* 3072-bit => key size 416-bit */
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}
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else if (groupsize <= 512) {
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return 60; /* 4096-bit => key size 480-bit */
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}
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else if (groupsize <= 768) {
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return 67; /* 6144-bit => key size 536-bit */
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}
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else if (groupsize <= 1024) {
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return 77; /* 8192-bit => key size 616-bit */
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}
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else {
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return 0;
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}
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}
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int dh_generate_key(prng_state *prng, int wprng, dh_key *key)
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{
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unsigned char *buf;
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unsigned long keysize;
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int err, max_iterations = LTC_PK_MAX_RETRIES;
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LTC_ARGCHK(key != NULL);
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LTC_ARGCHK(ltc_mp.name != NULL);
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/* good prng? */
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if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
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return err;
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}
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keysize = _dh_groupsize_to_keysize(mp_unsigned_bin_size(key->prime));
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if (keysize == 0) {
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err = CRYPT_INVALID_KEYSIZE;
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goto freemp;
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}
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/* allocate buffer */
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buf = XMALLOC(keysize);
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if (buf == NULL) {
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err = CRYPT_MEM;
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goto freemp;
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}
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key->type = PK_PRIVATE;
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do {
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/* make up random buf */
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if (prng_descriptor[wprng].read(buf, keysize, prng) != keysize) {
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err = CRYPT_ERROR_READPRNG;
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goto freebuf;
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}
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/* load the x value - private key */
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if ((err = mp_read_unsigned_bin(key->x, buf, keysize)) != CRYPT_OK) {
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goto freebuf;
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}
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/* compute the y value - public key */
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if ((err = mp_exptmod(key->base, key->x, key->prime, key->y)) != CRYPT_OK) {
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goto freebuf;
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}
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err = dh_check_pubkey(key);
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} while (err != CRYPT_OK && max_iterations-- > 0);
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freebuf:
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zeromem(buf, keysize);
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XFREE(buf);
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freemp:
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if (err != CRYPT_OK) dh_free(key);
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return err;
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}
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#endif /* LTC_MDH */
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/* ref: HEAD -> master, tag: v1.18.2 */
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/* git commit: 7e7eb695d581782f04b24dc444cbfde86af59853 */
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/* commit time: 2018-07-01 22:49:01 +0200 */
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