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108 lines
4.3 KiB
C
108 lines
4.3 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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/**
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@file rsa_make_key.c
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RSA key generation, Tom St Denis
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*/
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#ifdef LTC_MRSA
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/**
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Create an RSA key
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@param prng An active PRNG state
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@param wprng The index of the PRNG desired
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@param size The size of the modulus (key size) desired (octets)
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@param e The "e" value (public key). e==65537 is a good choice
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@param key [out] Destination of a newly created private key pair
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@return CRYPT_OK if successful, upon error all allocated ram is freed
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*/
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int rsa_make_key(prng_state *prng, int wprng, int size, long e, rsa_key *key)
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{
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void *p, *q, *tmp1, *tmp2, *tmp3;
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int err;
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LTC_ARGCHK(ltc_mp.name != NULL);
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LTC_ARGCHK(key != NULL);
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LTC_ARGCHK(size > 0);
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if ((e < 3) || ((e & 1) == 0)) {
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return CRYPT_INVALID_ARG;
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}
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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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if ((err = mp_init_multi(&p, &q, &tmp1, &tmp2, &tmp3, NULL)) != CRYPT_OK) {
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return err;
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}
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/* make primes p and q (optimization provided by Wayne Scott) */
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if ((err = mp_set_int(tmp3, e)) != CRYPT_OK) { goto cleanup; } /* tmp3 = e */
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/* make prime "p" */
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do {
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if ((err = rand_prime( p, size/2, prng, wprng)) != CRYPT_OK) { goto cleanup; }
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if ((err = mp_sub_d( p, 1, tmp1)) != CRYPT_OK) { goto cleanup; } /* tmp1 = p-1 */
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if ((err = mp_gcd( tmp1, tmp3, tmp2)) != CRYPT_OK) { goto cleanup; } /* tmp2 = gcd(p-1, e) */
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} while (mp_cmp_d( tmp2, 1) != 0); /* while e divides p-1 */
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/* make prime "q" */
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do {
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if ((err = rand_prime( q, size/2, prng, wprng)) != CRYPT_OK) { goto cleanup; }
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if ((err = mp_sub_d( q, 1, tmp1)) != CRYPT_OK) { goto cleanup; } /* tmp1 = q-1 */
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if ((err = mp_gcd( tmp1, tmp3, tmp2)) != CRYPT_OK) { goto cleanup; } /* tmp2 = gcd(q-1, e) */
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} while (mp_cmp_d( tmp2, 1) != 0); /* while e divides q-1 */
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/* tmp1 = lcm(p-1, q-1) */
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if ((err = mp_sub_d( p, 1, tmp2)) != CRYPT_OK) { goto cleanup; } /* tmp2 = p-1 */
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/* tmp1 = q-1 (previous do/while loop) */
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if ((err = mp_lcm( tmp1, tmp2, tmp1)) != CRYPT_OK) { goto cleanup; } /* tmp1 = lcm(p-1, q-1) */
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/* make key */
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if ((err = mp_init_multi(&key->e, &key->d, &key->N, &key->dQ, &key->dP, &key->qP, &key->p, &key->q, NULL)) != CRYPT_OK) {
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goto errkey;
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}
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if ((err = mp_set_int( key->e, e)) != CRYPT_OK) { goto errkey; } /* key->e = e */
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if ((err = mp_invmod( key->e, tmp1, key->d)) != CRYPT_OK) { goto errkey; } /* key->d = 1/e mod lcm(p-1,q-1) */
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if ((err = mp_mul( p, q, key->N)) != CRYPT_OK) { goto errkey; } /* key->N = pq */
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/* optimize for CRT now */
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/* find d mod q-1 and d mod p-1 */
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if ((err = mp_sub_d( p, 1, tmp1)) != CRYPT_OK) { goto errkey; } /* tmp1 = q-1 */
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if ((err = mp_sub_d( q, 1, tmp2)) != CRYPT_OK) { goto errkey; } /* tmp2 = p-1 */
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if ((err = mp_mod( key->d, tmp1, key->dP)) != CRYPT_OK) { goto errkey; } /* dP = d mod p-1 */
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if ((err = mp_mod( key->d, tmp2, key->dQ)) != CRYPT_OK) { goto errkey; } /* dQ = d mod q-1 */
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if ((err = mp_invmod( q, p, key->qP)) != CRYPT_OK) { goto errkey; } /* qP = 1/q mod p */
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if ((err = mp_copy( p, key->p)) != CRYPT_OK) { goto errkey; }
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if ((err = mp_copy( q, key->q)) != CRYPT_OK) { goto errkey; }
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/* set key type (in this case it's CRT optimized) */
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key->type = PK_PRIVATE;
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/* return ok and free temps */
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err = CRYPT_OK;
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goto cleanup;
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errkey:
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rsa_free(key);
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cleanup:
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mp_clear_multi(tmp3, tmp2, tmp1, q, p, NULL);
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return err;
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}
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#endif
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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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