/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, tomstdenis@gmail.com, http://libtom.org */ /* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b * * All curves taken from NIST recommendation paper of July 1999 * Available at http://csrc.nist.gov/cryptval/dss.htm */ #include "tomcrypt.h" /** @file ecc_make_key.c ECC Crypto, Tom St Denis */ #ifdef LTC_MECC /** Make a new ECC key @param prng An active PRNG state @param wprng The index of the PRNG you wish to use @param keysize The keysize for the new key (in octets from 20 to 65 bytes) @param key [out] Destination of the newly created key @return CRYPT_OK if successful, upon error all allocated memory will be freed */ int ecc_make_key(prng_state *prng, int wprng, int keysize, ecc_key *key) { int x, err; /* find key size */ for (x = 0; (keysize > ltc_ecc_sets[x].size) && (ltc_ecc_sets[x].size != 0); x++); keysize = ltc_ecc_sets[x].size; if (keysize > ECC_MAXSIZE || ltc_ecc_sets[x].size == 0) { return CRYPT_INVALID_KEYSIZE; } err = ecc_make_key_ex(prng, wprng, key, <c_ecc_sets[x]); key->idx = x; return err; } int ecc_make_key_ex(prng_state *prng, int wprng, ecc_key *key, const ltc_ecc_set_type *dp) { int err; ecc_point *base; void *prime, *order; unsigned char *buf; int keysize; LTC_ARGCHK(key != NULL); LTC_ARGCHK(ltc_mp.name != NULL); LTC_ARGCHK(dp != NULL); /* good prng? */ if ((err = prng_is_valid(wprng)) != CRYPT_OK) { return err; } key->idx = -1; key->dp = dp; keysize = dp->size; /* allocate ram */ base = NULL; buf = XMALLOC(ECC_MAXSIZE); if (buf == NULL) { return CRYPT_MEM; } /* make up random string */ if (prng_descriptor[wprng].read(buf, (unsigned long)keysize, prng) != (unsigned long)keysize) { err = CRYPT_ERROR_READPRNG; goto ERR_BUF; } /* setup the key variables */ if ((err = mp_init_multi(&key->pubkey.x, &key->pubkey.y, &key->pubkey.z, &key->k, &prime, &order, NULL)) != CRYPT_OK) { goto ERR_BUF; } base = ltc_ecc_new_point(); if (base == NULL) { err = CRYPT_MEM; goto errkey; } /* read in the specs for this key */ if ((err = mp_read_radix(prime, (char *)key->dp->prime, 16)) != CRYPT_OK) { goto errkey; } if ((err = mp_read_radix(order, (char *)key->dp->order, 16)) != CRYPT_OK) { goto errkey; } if ((err = mp_read_radix(base->x, (char *)key->dp->Gx, 16)) != CRYPT_OK) { goto errkey; } if ((err = mp_read_radix(base->y, (char *)key->dp->Gy, 16)) != CRYPT_OK) { goto errkey; } if ((err = mp_set(base->z, 1)) != CRYPT_OK) { goto errkey; } if ((err = mp_read_unsigned_bin(key->k, (unsigned char *)buf, keysize)) != CRYPT_OK) { goto errkey; } /* the key should be smaller than the order of base point */ if (mp_cmp(key->k, order) != LTC_MP_LT) { if((err = mp_mod(key->k, order, key->k)) != CRYPT_OK) { goto errkey; } } /* make the public key */ if ((err = ltc_mp.ecc_ptmul(key->k, base, &key->pubkey, prime, 1)) != CRYPT_OK) { goto errkey; } key->type = PK_PRIVATE; /* free up ram */ err = CRYPT_OK; goto cleanup; errkey: mp_clear_multi(key->pubkey.x, key->pubkey.y, key->pubkey.z, key->k, NULL); cleanup: ltc_ecc_del_point(base); mp_clear_multi(prime, order, NULL); ERR_BUF: #ifdef LTC_CLEAN_STACK zeromem(buf, ECC_MAXSIZE); #endif XFREE(buf); return err; } #endif /* $Source$ */ /* $Revision$ */ /* $Date$ */