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/* Copyright 2015 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "dcrypto.h"
#include <stdint.h>
/* p256_base_point_mul sets {out_x,out_y} = nG, where n is < the
* order of the group. */
int DCRYPTO_p256_base_point_mul(p256_int *out_x, p256_int *out_y,
const p256_int *n)
{
if (p256_is_zero(n) != 0) {
p256_clear(out_x);
p256_clear(out_y);
return 0;
}
return dcrypto_p256_base_point_mul(n, out_x, out_y);
}
/* DCRYPTO_p256_point_mul sets {out_x,out_y} = n*{in_x,in_y}, where n is <
* the order of the group. */
int DCRYPTO_p256_point_mul(p256_int *out_x, p256_int *out_y,
const p256_int *n, const p256_int *in_x,
const p256_int *in_y)
{
if (p256_is_zero(n) != 0) {
p256_clear(out_x);
p256_clear(out_y);
return 0;
}
return dcrypto_p256_point_mul(n, in_x, in_y, out_x, out_y);
}
/**
* Key selection based on FIPS-186-4, section B.4.2 (Key Pair
* Generation by Testing Candidates).
*/
int DCRYPTO_p256_key_from_bytes(p256_int *x, p256_int *y, p256_int *d,
const uint8_t key_bytes[P256_NBYTES])
{
p256_int key;
p256_from_bin(key_bytes, &key);
/**
* We need key to be in the range 0 < key < SECP256r1 - 1.
* To achieve that, first check key < SECP256r1 - 2, and
* then add 1 to key. Since key is unsigned number this will
* bring key in proper range.
*/
if (p256_lt_blinded(&key, &SECP256r1_nMin2) >= 0)
return 0;
p256_add_d(&key, 1, d);
always_memset(&key, 0, sizeof(key));
if (x == NULL || y == NULL)
return 1;
return dcrypto_p256_base_point_mul(d, x, y);
}
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