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 katja_make_key.c 15 Katja key generation, Tom St Denis 16 */ 17 18 #ifdef MKAT 19 20 /** 21 Create a Katja 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 key [out] Destination of a newly created private key pair 26 @return CRYPT_OK if successful, upon error all allocated ram is freed 27 */ 28 int katja_make_key(prng_state *prng, int wprng, int size, katja_key *key) 29 { 30 void *p, *q, *tmp1, *tmp2; 31 int err; 32 33 LTC_ARGCHK(key != NULL); 34 LTC_ARGCHK(ltc_mp.name != NULL); 35 36 if ((size < (MIN_KAT_SIZE/8)) || (size > (MAX_KAT_SIZE/8))) { 37 return CRYPT_INVALID_KEYSIZE; 38 } 39 40 if ((err = prng_is_valid(wprng)) != CRYPT_OK) { 41 return err; 42 } 43 44 if ((err = mp_init_multi(&p, &q, &tmp1, &tmp2, NULL)) != CRYPT_OK) { 45 return err; 46 } 47 48 /* divide size by three */ 49 size = (((size << 3) / 3) + 7) >> 3; 50 51 /* make prime "q" (we negate size to make q == 3 mod 4) */ 52 if ((err = rand_prime(q, -size, prng, wprng)) != CRYPT_OK) { goto done; } 53 if ((err = mp_sub_d(q, 1, tmp1)) != CRYPT_OK) { goto done; } 54 55 /* make prime "p" */ 56 do { 57 if ((err = rand_prime(p, size+1, prng, wprng)) != CRYPT_OK) { goto done; } 58 if ((err = mp_gcd(p, tmp1, tmp2)) != CRYPT_OK) { goto done; } 59 } while (mp_cmp_d(tmp2, 1) != LTC_MP_EQ); 60 61 /* make key */ 62 if ((err = mp_init_multi(&key->d, &key->N, &key->dQ, &key->dP, 63 &key->qP, &key->p, &key->q, &key->pq, NULL)) != CRYPT_OK) { 64 goto error; 65 } 66 67 /* n=p^2q and 1/n mod pq */ 68 if ((err = mp_copy( p, key->p)) != CRYPT_OK) { goto error2; } 69 if ((err = mp_copy( q, key->q)) != CRYPT_OK) { goto error2; } 70 if ((err = mp_mul(key->p, key->q, key->pq)) != CRYPT_OK) { goto error2; } /* tmp1 = pq */ 71 if ((err = mp_mul(key->pq, key->p, key->N)) != CRYPT_OK) { goto error2; } /* N = p^2q */ 72 if ((err = mp_sub_d( p, 1, tmp1)) != CRYPT_OK) { goto error2; } /* tmp1 = q-1 */ 73 if ((err = mp_sub_d( q, 1, tmp2)) != CRYPT_OK) { goto error2; } /* tmp2 = p-1 */ 74 if ((err = mp_lcm(tmp1, tmp2, key->d)) != CRYPT_OK) { goto error2; } /* tmp1 = lcd(p-1,q-1) */ 75 if ((err = mp_invmod( key->N, key->d, key->d)) != CRYPT_OK) { goto error2; } /* key->d = 1/N mod pq */ 76 77 /* optimize for CRT now */ 78 /* find d mod q-1 and d mod p-1 */ 79 if ((err = mp_mod( key->d, tmp1, key->dP)) != CRYPT_OK) { goto error2; } /* dP = d mod p-1 */ 80 if ((err = mp_mod( key->d, tmp2, key->dQ)) != CRYPT_OK) { goto error2; } /* dQ = d mod q-1 */ 81 if ((err = mp_invmod( q, p, key->qP)) != CRYPT_OK) { goto error2; } /* qP = 1/q mod p */ 82 83 /* set key type (in this case it's CRT optimized) */ 84 key->type = PK_PRIVATE; 85 86 /* return ok and free temps */ 87 err = CRYPT_OK; 88 goto done; 89 error2: 90 mp_clear_multi( key->d, key->N, key->dQ, key->dP, key->qP, key->p, key->q, key->pq, NULL); 91 error: 92 done: 93 mp_clear_multi( tmp2, tmp1, p, q, NULL); 94 return err; 95 } 96 97 #endif 98 99 /* $Source: /cvs/libtom/libtomcrypt/src/pk/katja/katja_make_key.c,v $ */ 100 /* $Revision: 1.10 $ */ 101 /* $Date: 2006/03/31 14:15:35 $ */ 102
