BN_MOD_MUL_MONTGOMERY(3ossl) OpenSSL BN_MOD_MUL_MONTGOMERY(3ossl)
NAME
BN_mod_mul_montgomery, BN_MONT_CTX_new, BN_MONT_CTX_free,
BN_MONT_CTX_set, BN_MONT_CTX_copy, BN_from_montgomery, BN_to_montgomery
- Montgomery multiplication
SYNOPSIS
#include <openssl/bn.h>
BN_MONT_CTX *BN_MONT_CTX_new(void);
void BN_MONT_CTX_free(BN_MONT_CTX *mont);
int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *m, BN_CTX *ctx);
BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to, BN_MONT_CTX *from);
int BN_mod_mul_montgomery(BIGNUM *r, BIGNUM *a, BIGNUM *b,
BN_MONT_CTX *mont, BN_CTX *ctx);
int BN_from_montgomery(BIGNUM *r, BIGNUM *a, BN_MONT_CTX *mont,
BN_CTX *ctx);
int BN_to_montgomery(BIGNUM *r, BIGNUM *a, BN_MONT_CTX *mont,
BN_CTX *ctx);
DESCRIPTION
These functions implement Montgomery multiplication. They are used
automatically when BN_mod_exp(3) is called with suitable input, but
they may be useful when several operations are to be performed using
the same modulus.
BN_MONT_CTX_new() allocates and initializes a BN_MONT_CTX structure.
BN_MONT_CTX_set() sets up the mont structure from the modulus m by
precomputing its inverse and a value R.
BN_MONT_CTX_copy() copies the BN_MONT_CTX from to to.
BN_MONT_CTX_free() frees the components of the BN_MONT_CTX, and, if it
was created by BN_MONT_CTX_new(), also the structure itself. If mont
is NULL, nothing is done.
BN_mod_mul_montgomery(3) computes Mont(a,b):=a*b*R^-1 and places the
result in r.
BN_from_montgomery() performs the Montgomery reduction r = a*R^-1.
BN_to_montgomery() computes Mont(a,R^2), i.e. a*R. Note that a must be
nonnegative and smaller than the modulus.
For all functions, ctx is a previously allocated BN_CTX used for
temporary variables.
RETURN VALUES
BN_MONT_CTX_new() returns the newly allocated BN_MONT_CTX, and NULL on
error.
BN_MONT_CTX_free() has no return value.
For the other functions, 1 is returned for success, 0 on error. The
error codes can be obtained by ERR_get_error(3).
WARNINGS
The inputs must be reduced modulo m, otherwise the result will be
outside the expected range.
SEE ALSO
ERR_get_error(3), BN_add(3), BN_CTX_new(3)
HISTORY
BN_MONT_CTX_init() was removed in OpenSSL 1.1.0
COPYRIGHT
Copyright 2000-2020 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>.
3.4.0 2024-10-29 BN_MOD_MUL_MONTGOMERY(3ossl)
openssl 3.4.0 - Generated Sat Nov 2 07:27:29 CDT 2024