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Add secp256k1_scalar_inverse_var which delegates to GMP

This commit is contained in:
Pieter Wuille 2014-11-26 16:04:24 +01:00
parent b5c9ee756f
commit d1502eb459
3 changed files with 22 additions and 1 deletions
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3
configure.ac
View File

@ -223,7 +223,8 @@ case $set_bignum in
gmp) gmp)
AC_DEFINE(HAVE_LIBGMP,1,[Define this symbol if libgmp is installed]) AC_DEFINE(HAVE_LIBGMP,1,[Define this symbol if libgmp is installed])
AC_DEFINE(USE_NUM_GMP, 1, [Define this symbol to use the gmp implementation]) AC_DEFINE(USE_NUM_GMP, 1, [Define this symbol to use the gmp implementation])
AC_DEFINE(USE_FIELD_INV_NUM, 1, [Define this symbol to use the USE_FIELD_INV_NUM implementation]) AC_DEFINE(USE_FIELD_INV_NUM, 1, [Define this symbol to use the num-based field inverse implementation])
AC_DEFINE(USE_SCALAR_INV_NUM, 1, [Define this symbol to use the num-based scalar inverse implementation])
;; ;;
*) *)
AC_MSG_ERROR([invalid bignum implementation]) AC_MSG_ERROR([invalid bignum implementation])

3
src/scalar.h
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@ -54,6 +54,9 @@ static void secp256k1_scalar_sqr(secp256k1_scalar_t *r, const secp256k1_scalar_t
/** Compute the inverse of a scalar (modulo the group order). */ /** Compute the inverse of a scalar (modulo the group order). */
static void secp256k1_scalar_inverse(secp256k1_scalar_t *r, const secp256k1_scalar_t *a); static void secp256k1_scalar_inverse(secp256k1_scalar_t *r, const secp256k1_scalar_t *a);
/** Compute the inverse of a scalar (modulo the group order), without constant-time guarantee. */
static void secp256k1_scalar_inverse_var(secp256k1_scalar_t *r, const secp256k1_scalar_t *a);
/** Compute the complement of a scalar (modulo the group order). */ /** Compute the complement of a scalar (modulo the group order). */
static void secp256k1_scalar_negate(secp256k1_scalar_t *r, const secp256k1_scalar_t *a); static void secp256k1_scalar_negate(secp256k1_scalar_t *r, const secp256k1_scalar_t *a);

17
src/scalar_impl.h
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@ -9,6 +9,7 @@
#include <string.h> #include <string.h>
#include "group.h"
#include "scalar.h" #include "scalar.h"
#if defined HAVE_CONFIG_H #if defined HAVE_CONFIG_H
@ -181,4 +182,20 @@ static void secp256k1_scalar_inverse(secp256k1_scalar_t *r, const secp256k1_scal
secp256k1_scalar_mul(r, t, &x6); /* 111111 */ secp256k1_scalar_mul(r, t, &x6); /* 111111 */
} }
static void secp256k1_scalar_inverse_var(secp256k1_scalar_t *r, const secp256k1_scalar_t *x) {
#if defined(USE_SCALAR_INV_BUILTIN)
secp256k1_scalar_inverse(r, x);
#elif defined(USE_SCALAR_INV_NUM)
unsigned char b[32];
secp256k1_scalar_get_b32(b, x);
secp256k1_num_t n;
secp256k1_num_set_bin(&n, b, 32);
secp256k1_num_mod_inverse(&n, &n, &secp256k1_ge_consts->order);
secp256k1_num_get_bin(b, 32, &n);
secp256k1_scalar_set_b32(r, b, NULL);
#else
#error "Please select scalar inverse implementation"
#endif
}
#endif #endif