mirror of https://github.com/ethereum/go-ethereum
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
43 lines
2.2 KiB
43 lines
2.2 KiB
/**********************************************************************
|
|
* Copyright (c) 2013, 2014 Pieter Wuille *
|
|
* Distributed under the MIT software license, see the accompanying *
|
|
* file COPYING or http://www.opensource.org/licenses/mit-license.php.*
|
|
**********************************************************************/
|
|
|
|
#ifndef _SECP256K1_ECMULT_GEN_
|
|
#define _SECP256K1_ECMULT_GEN_
|
|
|
|
#include "scalar.h"
|
|
#include "group.h"
|
|
|
|
typedef struct {
|
|
/* For accelerating the computation of a*G:
|
|
* To harden against timing attacks, use the following mechanism:
|
|
* * Break up the multiplicand into groups of 4 bits, called n_0, n_1, n_2, ..., n_63.
|
|
* * Compute sum(n_i * 16^i * G + U_i, i=0..63), where:
|
|
* * U_i = U * 2^i (for i=0..62)
|
|
* * U_i = U * (1-2^63) (for i=63)
|
|
* where U is a point with no known corresponding scalar. Note that sum(U_i, i=0..63) = 0.
|
|
* For each i, and each of the 16 possible values of n_i, (n_i * 16^i * G + U_i) is
|
|
* precomputed (call it prec(i, n_i)). The formula now becomes sum(prec(i, n_i), i=0..63).
|
|
* None of the resulting prec group elements have a known scalar, and neither do any of
|
|
* the intermediate sums while computing a*G.
|
|
*/
|
|
secp256k1_ge_storage (*prec)[64][16]; /* prec[j][i] = 16^j * i * G + U_i */
|
|
secp256k1_scalar blind;
|
|
secp256k1_gej initial;
|
|
} secp256k1_ecmult_gen_context;
|
|
|
|
static void secp256k1_ecmult_gen_context_init(secp256k1_ecmult_gen_context* ctx);
|
|
static void secp256k1_ecmult_gen_context_build(secp256k1_ecmult_gen_context* ctx, const secp256k1_callback* cb);
|
|
static void secp256k1_ecmult_gen_context_clone(secp256k1_ecmult_gen_context *dst,
|
|
const secp256k1_ecmult_gen_context* src, const secp256k1_callback* cb);
|
|
static void secp256k1_ecmult_gen_context_clear(secp256k1_ecmult_gen_context* ctx);
|
|
static int secp256k1_ecmult_gen_context_is_built(const secp256k1_ecmult_gen_context* ctx);
|
|
|
|
/** Multiply with the generator: R = a*G */
|
|
static void secp256k1_ecmult_gen(const secp256k1_ecmult_gen_context* ctx, secp256k1_gej *r, const secp256k1_scalar *a);
|
|
|
|
static void secp256k1_ecmult_gen_blind(secp256k1_ecmult_gen_context *ctx, const unsigned char *seed32);
|
|
|
|
#endif
|
|
|