BN_mod_exp_mont, BN_mod_exp_mont_consttime, BN_mod_exp_mont_consttime_x2 -
Montgomery exponentiation
#include <openssl/bn.h>
int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont);
int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
const BIGNUM *m, BN_CTX *ctx,
BN_MONT_CTX *in_mont);
int BN_mod_exp_mont_consttime_x2(BIGNUM *rr1, const BIGNUM *a1,
const BIGNUM *p1, const BIGNUM *m1,
BN_MONT_CTX *in_mont1, BIGNUM *rr2,
const BIGNUM *a2, const BIGNUM *p2,
const BIGNUM *m2, BN_MONT_CTX *in_mont2,
BN_CTX *ctx);
BN_mod_exp_mont() computes
a to the
p-th power modulo
m ("rr=a^p % m") using Montgomery multiplication.
in_mont is a Montgomery context and can be NULL. In the case
in_mont is NULL, it will be initialized within the function, so you can
save time on initialization if you provide it in advance.
BN_mod_exp_mont_consttime() computes
a to the
p-th power
modulo
m ("rr=a^p % m") using Montgomery multiplication. It
is a variant of
BN_mod_exp_mont(3) that uses fixed windows and the
special precomputation memory layout to limit data-dependency to a minimum to
protect secret exponents. It is called automatically when
BN_mod_exp_mont(3) is called with parameters
a,
p,
m, any of which have
BN_FLG_CONSTTIME flag.
BN_mod_exp_mont_consttime_x2() computes two independent exponentiations
a1 to the
p1-th power modulo
m1 ("rr1=a1^p1 %
m1") and
a2 to the
p2-th power modulo
m2
("rr2=a2^p2 % m2") using Montgomery multiplication. For some fixed
and equal modulus sizes
m1 and
m2 it uses optimizations that
allow to speedup two exponentiations. In all other cases the function reduces
to two calls of
BN_mod_exp_mont_consttime(3).
For all functions 1 is returned for success, 0 on error. The error codes can be
obtained by
ERR_get_error(3).
ERR_get_error(3),
BN_mod_exp_mont(3)
Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy in the
file LICENSE in the source distribution or at
<
https://www.openssl.org/source/license.html>.