BN_mod_mul_montgomery(3) OpenSSL BN_mod_mul_montgomery(3)
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() 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 OpenSSL license (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>.
1.1.1h 2020-09-22 BN_mod_mul_montgomery(3)
openssl 1.1.1h - Generated Thu Oct 1 19:10:22 CDT 2020