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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://libtomcrypt.com
*/
/* 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_import.c
ECC Crypto, Tom St Denis
*/
#ifdef MECC
static int is_point(ecc_key *key)
{
void *prime, *b, *t1, *t2;
int err;
if ((err = mp_init_multi(&prime, &b, &t1, &t2, NULL)) != CRYPT_OK) {
return err;
}
/* load prime and b */
if ((err = mp_read_radix(prime, key->dp->prime, 16)) != CRYPT_OK) { goto error; }
if ((err = mp_read_radix(b, key->dp->B, 16)) != CRYPT_OK) { goto error; }
/* compute y^2 */
if ((err = mp_sqr(key->pubkey.y, t1)) != CRYPT_OK) { goto error; }
/* compute x^3 */
if ((err = mp_sqr(key->pubkey.x, t2)) != CRYPT_OK) { goto error; }
if ((err = mp_mod(t2, prime, t2)) != CRYPT_OK) { goto error; }
if ((err = mp_mul(key->pubkey.x, t2, t2)) != CRYPT_OK) { goto error; }
/* compute y^2 - x^3 */
if ((err = mp_sub(t1, t2, t1)) != CRYPT_OK) { goto error; }
/* compute y^2 - x^3 + 3x */
if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; }
if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; }
if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; }
if ((err = mp_mod(t1, prime, t1)) != CRYPT_OK) { goto error; }
while (mp_cmp_d(t1, 0) == LTC_MP_LT) {
if ((err = mp_add(t1, prime, t1)) != CRYPT_OK) { goto error; }
}
while (mp_cmp(t1, prime) != LTC_MP_LT) {
if ((err = mp_sub(t1, prime, t1)) != CRYPT_OK) { goto error; }
}
/* compare to b */
if (mp_cmp(t1, b) != LTC_MP_EQ) {
err = CRYPT_INVALID_PACKET;
} else {
err = CRYPT_OK;
}
error:
mp_clear_multi(prime, b, t1, t2, NULL);
return err;
}
/**
Import an ECC key from a binary packet
@param in The packet to import
@param inlen The length of the packet
@param key [out] The destination of the import
@return CRYPT_OK if successful, upon error all allocated memory will be freed
*/
int ecc_import(const unsigned char *in, unsigned long inlen, ecc_key *key)
{
return ecc_import_ex(in, inlen, key, NULL);
}
/**
Import an ECC key from a binary packet, using user supplied domain params rather than one of the NIST ones
@param in The packet to import
@param inlen The length of the packet
@param key [out] The destination of the import
@param dp pointer to user supplied params; must be the same as the params used when exporting
@return CRYPT_OK if successful, upon error all allocated memory will be freed
*/
int ecc_import_ex(const unsigned char *in, unsigned long inlen, ecc_key *key, const ltc_ecc_set_type *dp)
{
unsigned long key_size;
unsigned char flags[1];
int err;
LTC_ARGCHK(in != NULL);
LTC_ARGCHK(key != NULL);
LTC_ARGCHK(ltc_mp.name != NULL);
/* init key */
if (mp_init_multi(&key->pubkey.x, &key->pubkey.y, &key->pubkey.z, &key->k, NULL) != CRYPT_OK) {
return CRYPT_MEM;
}
/* find out what type of key it is */
if ((err = der_decode_sequence_multi(in, inlen,
LTC_ASN1_BIT_STRING, 1UL, &flags,
LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) {
goto done;
}
if (flags[0] == 1) {
/* private key */
key->type = PK_PRIVATE;
if ((err = der_decode_sequence_multi(in, inlen,
LTC_ASN1_BIT_STRING, 1UL, flags,
LTC_ASN1_SHORT_INTEGER, 1UL, &key_size,
LTC_ASN1_INTEGER, 1UL, key->pubkey.x,
LTC_ASN1_INTEGER, 1UL, key->pubkey.y,
LTC_ASN1_INTEGER, 1UL, key->k,
LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) {
goto done;
}
} else {
/* public key */
key->type = PK_PUBLIC;
if ((err = der_decode_sequence_multi(in, inlen,
LTC_ASN1_BIT_STRING, 1UL, flags,
LTC_ASN1_SHORT_INTEGER, 1UL, &key_size,
LTC_ASN1_INTEGER, 1UL, key->pubkey.x,
LTC_ASN1_INTEGER, 1UL, key->pubkey.y,
LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) {
goto done;
}
}
if (dp == NULL) {
/* find the idx */
for (key->idx = 0; ltc_ecc_sets[key->idx].size && (unsigned long)ltc_ecc_sets[key->idx].size != key_size; ++key->idx);
if (ltc_ecc_sets[key->idx].size == 0) {
err = CRYPT_INVALID_PACKET;
goto done;
}
key->dp = <c_ecc_sets[key->idx];
} else {
key->idx = -1;
key->dp = dp;
}
/* set z */
if ((err = mp_set(key->pubkey.z, 1)) != CRYPT_OK) { goto done; }
/* is it a point on the curve? */
if ((err = is_point(key)) != CRYPT_OK) {
goto done;
}
/* we're good */
return CRYPT_OK;
done:
mp_clear_multi(key->pubkey.x, key->pubkey.y, key->pubkey.z, key->k, NULL);
return err;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_import.c,v $ */
/* $Revision: 1.11 $ */
/* $Date: 2006/12/04 02:19:48 $ */
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