Skip to content

Commit

Permalink
make SECP256K1_SCALAR_CONST reduce modulo exhaustive group order
Browse files Browse the repository at this point in the history
  • Loading branch information
sipa committed Nov 4, 2023
1 parent 2140da9 commit ba523be
Showing 1 changed file with 9 additions and 2 deletions.
11 changes: 9 additions & 2 deletions src/scalar_low.h
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/***********************************************************************
* Copyright (c) 2015 Andrew Poelstra *
* Copyright (c) 2015, 2022 Andrew Poelstra, Pieter Wuille *
* Distributed under the MIT software license, see the accompanying *
* file COPYING or https://www.opensource.org/licenses/mit-license.php.*
***********************************************************************/
Expand All @@ -12,6 +12,13 @@
/** A scalar modulo the group order of the secp256k1 curve. */
typedef uint32_t secp256k1_scalar;

#define SECP256K1_SCALAR_CONST(d7, d6, d5, d4, d3, d2, d1, d0) (d0)
/* A compile-time constant equal to 2^32 (modulo order). */
#define SCALAR_2P32 ((0xffffffffUL % EXHAUSTIVE_TEST_ORDER) + 1U)

/* Compute a*2^32 + b (modulo order). */
#define SCALAR_HORNER(a, b) (((uint64_t)(a) * SCALAR_2P32 + (b)) % EXHAUSTIVE_TEST_ORDER)

/* Evaluates to the provided 256-bit constant reduced modulo order. */
#define SECP256K1_SCALAR_CONST(d7, d6, d5, d4, d3, d2, d1, d0) SCALAR_HORNER(SCALAR_HORNER(SCALAR_HORNER(SCALAR_HORNER(SCALAR_HORNER(SCALAR_HORNER(SCALAR_HORNER((d7), (d6)), (d5)), (d4)), (d3)), (d2)), (d1)), (d0))

#endif /* SECP256K1_SCALAR_REPR_H */

0 comments on commit ba523be

Please sign in to comment.