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/* 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
/* $Source$ */
/* $Revision$ */
/* $Date$ */
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