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Expose generator in pedersen/rangeproof API

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This commit is contained in:
Pieter Wuille
2016-07-06 13:46:23 +02:00
committed by Tim Ruffing
parent 360e218043
commit f6c84a02f3
8 changed files with 119 additions and 90 deletions
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21
src/modules/rangeproof/pedersen_impl.h
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@@ -17,19 +17,6 @@
#include "scalar.h"
#include "util.h"
/** Alternative generator for secp256k1.
* This is the sha256 of 'g' after DER encoding (without compression),
* which happens to be a point on the curve.
* sage: G2 = EllipticCurve ([F (0), F (7)]).lift_x(int(hashlib.sha256('0479be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8'.decode('hex')).hexdigest(),16))
* sage: '%x %x'%G2.xy()
*/
static const secp256k1_ge secp256k1_ge_const_g2 = SECP256K1_GE_CONST(
0x50929b74UL, 0xc1a04954UL, 0xb78b4b60UL, 0x35e97a5eUL,
0x078a5a0fUL, 0x28ec96d5UL, 0x47bfee9aUL, 0xce803ac0UL,
0x31d3c686UL, 0x3973926eUL, 0x049e637cUL, 0xb1b5f40aUL,
0x36dac28aUL, 0xf1766968UL, 0xc30c2313UL, 0xf3a38904UL
);
static void secp256k1_pedersen_scalar_set_u64(secp256k1_scalar *sec, uint64_t value) {
unsigned char data[32];
int i;
@@ -44,18 +31,18 @@ static void secp256k1_pedersen_scalar_set_u64(secp256k1_scalar *sec, uint64_t va
memset(data, 0, 32);
}
static void secp256k1_pedersen_ecmult_small(secp256k1_gej *r, uint64_t gn) {
static void secp256k1_pedersen_ecmult_small(secp256k1_gej *r, uint64_t gn, const secp256k1_ge* genp) {
secp256k1_scalar s;
secp256k1_pedersen_scalar_set_u64(&s, gn);
secp256k1_ecmult_const(r, &secp256k1_ge_const_g2, &s, 64);
secp256k1_ecmult_const(r, genp, &s, 64);
secp256k1_scalar_clear(&s);
}
/* sec * G + value * G2. */
SECP256K1_INLINE static void secp256k1_pedersen_ecmult(const secp256k1_ecmult_gen_context *ecmult_gen_ctx, secp256k1_gej *rj, const secp256k1_scalar *sec, uint64_t value) {
SECP256K1_INLINE static void secp256k1_pedersen_ecmult(const secp256k1_ecmult_gen_context *ecmult_gen_ctx, secp256k1_gej *rj, const secp256k1_scalar *sec, uint64_t value, const secp256k1_ge* genp) {
secp256k1_gej vj;
secp256k1_ecmult_gen(ecmult_gen_ctx, rj, sec);
secp256k1_pedersen_ecmult_small(&vj, value);
secp256k1_pedersen_ecmult_small(&vj, value, genp);
/* FIXME: constant time. */
secp256k1_gej_add_var(rj, rj, &vj, NULL);
secp256k1_gej_clear(&vj);