mirror of https://github.com/status-im/op-geth.git
57 lines
2.2 KiB
C
57 lines
2.2 KiB
C
|
// Copyright 2015 The go-ethereum Authors
|
||
|
|
// This file is part of the go-ethereum library.
|
||
|
|
//
|
||
|
|
// The go-ethereum library is free software: you can redistribute it and/or modify
|
||
|
|
// it under the terms of the GNU Lesser General Public License as published by
|
||
|
|
// the Free Software Foundation, either version 3 of the License, or
|
||
|
|
// (at your option) any later version.
|
||
|
|
//
|
||
|
|
// The go-ethereum library is distributed in the hope that it will be useful,
|
||
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||
|
|
// GNU Lesser General Public License for more details.
|
||
|
|
//
|
||
|
|
// You should have received a copy of the GNU Lesser General Public License
|
||
|
|
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
|
||
|
|
|
||
|
|
/** Multiply point by scalar in constant time.
|
||
|
|
* Returns: 1: multiplication was successful
|
||
|
|
* 0: scalar was invalid (zero or overflow)
|
||
|
|
* Args: ctx: pointer to a context object (cannot be NULL)
|
||
|
|
* Out: point: the multiplied point (usually secret)
|
||
|
|
* In: point: pointer to a 64-byte bytepublic point,
|
||
|
|
encoded as two 256bit big-endian numbers.
|
||
|
|
* scalar: a 32-byte scalar with which to multiply the point
|
||
|
|
*/
|
||
|
|
int secp256k1_pubkey_scalar_mul(const secp256k1_context* ctx, unsigned char *point, const unsigned char *scalar) {
|
||
|
|
int ret = 0;
|
||
|
|
int overflow = 0;
|
||
|
|
secp256k1_fe feX, feY;
|
||
|
|
secp256k1_gej res;
|
||
|
|
secp256k1_ge ge;
|
||
|
|
secp256k1_scalar s;
|
||
|
|
ARG_CHECK(point != NULL);
|
||
|
|
ARG_CHECK(scalar != NULL);
|
||
|
|
(void)ctx;
|
||
|
|
|
||
|
|
secp256k1_fe_set_b32(&feX, point);
|
||
|
|
secp256k1_fe_set_b32(&feY, point+32);
|
||
|
|
secp256k1_ge_set_xy(&ge, &feX, &feY);
|
||
|
|
secp256k1_scalar_set_b32(&s, scalar, &overflow);
|
||
|
|
if (overflow || secp256k1_scalar_is_zero(&s)) {
|
||
|
|
ret = 0;
|
||
|
|
} else {
|
||
|
|
secp256k1_ecmult_const(&res, &ge, &s);
|
||
|
|
secp256k1_ge_set_gej(&ge, &res);
|
||
|
|
/* Note: can't use secp256k1_pubkey_save here because it is not constant time. */
|
||
|
|
secp256k1_fe_normalize(&ge.x);
|
||
|
|
secp256k1_fe_normalize(&ge.y);
|
||
|
|
secp256k1_fe_get_b32(point, &ge.x);
|
||
|
|
secp256k1_fe_get_b32(point+32, &ge.y);
|
||
|
|
ret = 1;
|
||
|
|
}
|
||
|
|
secp256k1_scalar_clear(&s);
|
||
|
|
return ret;
|
||
|
|
}
|
||
|
|
|