60 lines
1.6 KiB
C
60 lines
1.6 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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#include "tomcrypt_private.h"
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/* origin of this code - OLPC */
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#ifdef LTC_MECC
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/**
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Verify a key according to ANSI spec
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@param key The key to validate
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@return CRYPT_OK if successful
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*/
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int ltc_ecc_verify_key(const ecc_key *key)
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{
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int err, inf;
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ecc_point *point;
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void *prime = key->dp.prime;
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void *order = key->dp.order;
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void *a = key->dp.A;
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/* Test 1: Are the x and y points of the public key in the field? */
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if (ltc_mp.compare_d(key->pubkey.z, 1) == LTC_MP_EQ) {
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if ((ltc_mp.compare(key->pubkey.x, prime) != LTC_MP_LT) ||
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(ltc_mp.compare(key->pubkey.y, prime) != LTC_MP_LT) ||
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(ltc_mp.compare_d(key->pubkey.x, 0) == LTC_MP_LT) ||
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(ltc_mp.compare_d(key->pubkey.y, 0) == LTC_MP_LT) ||
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(ltc_mp_iszero(key->pubkey.x) && ltc_mp_iszero(key->pubkey.y))
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)
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{
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err = CRYPT_INVALID_PACKET;
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goto done2;
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}
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}
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/* Test 2: is the public key on the curve? */
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if ((err = ltc_ecc_is_point(&key->dp, key->pubkey.x, key->pubkey.y)) != CRYPT_OK) { goto done2; }
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/* Test 3: does nG = O? (n = order, O = point at infinity, G = public key) */
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point = ltc_ecc_new_point();
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if ((err = ltc_ecc_mulmod(order, &(key->pubkey), point, a, prime, 1)) != CRYPT_OK) { goto done1; }
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err = ltc_ecc_is_point_at_infinity(point, prime, &inf);
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if (err != CRYPT_OK || inf) {
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err = CRYPT_ERROR;
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}
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else {
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err = CRYPT_OK;
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}
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done1:
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ltc_ecc_del_point(point);
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done2:
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return err;
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}
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#endif
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