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 * Tom St Denis, tomstdenis (at) gmail.com, http://libtomcrypt.com 10 */ 11 #include "tomcrypt.h" 12 13 /** 14 @file rsa_make_key.c 15 RSA key generation, Tom St Denis 16 */ 17 18 #ifdef MRSA 19 20 /** 21 Create an RSA key 22 @param prng An active PRNG state 23 @param wprng The index of the PRNG desired 24 @param size The size of the modulus (key size) desired (octets) 25 @param e The "e" value (public key). e==65537 is a good choice 26 @param key [out] Destination of a newly created private key pair 27 @return CRYPT_OK if successful, upon error all allocated ram is freed 28 */ 29 int rsa_make_key(prng_state *prng, int wprng, int size, long e, rsa_key *key) 30 { 31 void *p, *q, *tmp1, *tmp2, *tmp3; 32 int err; 33 34 LTC_ARGCHK(ltc_mp.name != NULL); 35 LTC_ARGCHK(key != NULL); 36 37 if ((size < (MIN_RSA_SIZE/8)) || (size > (MAX_RSA_SIZE/8))) { 38 return CRYPT_INVALID_KEYSIZE; 39 } 40 41 if ((e < 3) || ((e & 1) == 0)) { 42 return CRYPT_INVALID_ARG; 43 } 44 45 if ((err = prng_is_valid(wprng)) != CRYPT_OK) { 46 return err; 47 } 48 49 if ((err = mp_init_multi(&p, &q, &tmp1, &tmp2, &tmp3, NULL)) != CRYPT_OK) { 50 return err; 51 } 52 53 /* make primes p and q (optimization provided by Wayne Scott) */ 54 if ((err = mp_set_int(tmp3, e)) != CRYPT_OK) { goto errkey; } /* tmp3 = e */ 55 56 /* make prime "p" */ 57 do { 58 if ((err = rand_prime( p, size/2, prng, wprng)) != CRYPT_OK) { goto errkey; } 59 if ((err = mp_sub_d( p, 1, tmp1)) != CRYPT_OK) { goto errkey; } /* tmp1 = p-1 */ 60 if ((err = mp_gcd( tmp1, tmp3, tmp2)) != CRYPT_OK) { goto errkey; } /* tmp2 = gcd(p-1, e) */ 61 } while (mp_cmp_d( tmp2, 1) != 0); /* while e divides p-1 */ 62 63 /* make prime "q" */ 64 do { 65 if ((err = rand_prime( q, size/2, prng, wprng)) != CRYPT_OK) { goto errkey; } 66 if ((err = mp_sub_d( q, 1, tmp1)) != CRYPT_OK) { goto errkey; } /* tmp1 = q-1 */ 67 if ((err = mp_gcd( tmp1, tmp3, tmp2)) != CRYPT_OK) { goto errkey; } /* tmp2 = gcd(q-1, e) */ 68 } while (mp_cmp_d( tmp2, 1) != 0); /* while e divides q-1 */ 69 70 /* tmp1 = lcm(p-1, q-1) */ 71 if ((err = mp_sub_d( p, 1, tmp2)) != CRYPT_OK) { goto errkey; } /* tmp2 = p-1 */ 72 /* tmp1 = q-1 (previous do/while loop) */ 73 if ((err = mp_lcm( tmp1, tmp2, tmp1)) != CRYPT_OK) { goto errkey; } /* tmp1 = lcm(p-1, q-1) */ 74 75 /* make key */ 76 if ((err = mp_init_multi(&key->e, &key->d, &key->N, &key->dQ, &key->dP, &key->qP, &key->p, &key->q, NULL)) != CRYPT_OK) { 77 goto errkey; 78 } 79 80 if ((err = mp_set_int( key->e, e)) != CRYPT_OK) { goto errkey; } /* key->e = e */ 81 if ((err = mp_invmod( key->e, tmp1, key->d)) != CRYPT_OK) { goto errkey; } /* key->d = 1/e mod lcm(p-1,q-1) */ 82 if ((err = mp_mul( p, q, key->N)) != CRYPT_OK) { goto errkey; } /* key->N = pq */ 83 84 /* optimize for CRT now */ 85 /* find d mod q-1 and d mod p-1 */ 86 if ((err = mp_sub_d( p, 1, tmp1)) != CRYPT_OK) { goto errkey; } /* tmp1 = q-1 */ 87 if ((err = mp_sub_d( q, 1, tmp2)) != CRYPT_OK) { goto errkey; } /* tmp2 = p-1 */ 88 if ((err = mp_mod( key->d, tmp1, key->dP)) != CRYPT_OK) { goto errkey; } /* dP = d mod p-1 */ 89 if ((err = mp_mod( key->d, tmp2, key->dQ)) != CRYPT_OK) { goto errkey; } /* dQ = d mod q-1 */ 90 if ((err = mp_invmod( q, p, key->qP)) != CRYPT_OK) { goto errkey; } /* qP = 1/q mod p */ 91 92 if ((err = mp_copy( p, key->p)) != CRYPT_OK) { goto errkey; } 93 if ((err = mp_copy( q, key->q)) != CRYPT_OK) { goto errkey; } 94 95 /* set key type (in this case it's CRT optimized) */ 96 key->type = PK_PRIVATE; 97 98 /* return ok and free temps */ 99 err = CRYPT_OK; 100 goto cleanup; 101 errkey: 102 mp_clear_multi(key->d, key->e, key->N, key->dQ, key->dP, key->qP, key->p, key->q, NULL); 103 cleanup: 104 mp_clear_multi(tmp3, tmp2, tmp1, p, q, NULL); 105 return err; 106 } 107 108 #endif 109 110 /* $Source: /cvs/libtom/libtomcrypt/src/pk/rsa/rsa_make_key.c,v $ */ 111 /* $Revision: 1.14 $ */ 112 /* $Date: 2006/12/04 22:23:27 $ */ 113
