BN_MOD_MUL_RECIPROCAL(3ossl) OpenSSL BN_MOD_MUL_RECIPROCAL(3ossl)
NAME
BN_mod_mul_reciprocal, BN_div_recp, BN_RECP_CTX_new, BN_RECP_CTX_free,
BN_RECP_CTX_set - modular multiplication using reciprocal
SYNOPSIS
#include <openssl/bn.h>
BN_RECP_CTX *BN_RECP_CTX_new(void);
void BN_RECP_CTX_free(BN_RECP_CTX *recp);
int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *m, BN_CTX *ctx);
int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *a, BN_RECP_CTX *recp,
BN_CTX *ctx);
int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
BN_RECP_CTX *recp, BN_CTX *ctx);
DESCRIPTION
BN_mod_mul_reciprocal(3) can be used to perform an efficient
BN_mod_mul(3) operation when the operation will be performed repeatedly
with the same modulus. It computes r=(a*b)%m using recp=1/m, which is
set as described below. ctx is a previously allocated BN_CTX used for
temporary variables.
BN_RECP_CTX_new() allocates and initializes a BN_RECP structure.
BN_RECP_CTX_free() frees the components of the BN_RECP, and, if it was
created by BN_RECP_CTX_new(), also the structure itself. If recp is
NULL, nothing is done.
BN_RECP_CTX_set() stores m in recp and sets it up for computing 1/m and
shifting it left by BN_num_bits(m)+1 to make it an integer. The result
and the number of bits it was shifted left will later be stored in
recp.
BN_div_recp() divides a by m using recp. It places the quotient in dv
and the remainder in rem.
The BN_RECP_CTX structure cannot be shared between threads.
RETURN VALUES
BN_RECP_CTX_new() returns the newly allocated BN_RECP_CTX, and NULL on
error.
BN_RECP_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).
SEE ALSO
ERR_get_error(3), BN_add(3), BN_CTX_new(3)
HISTORY
BN_RECP_CTX_init() was removed in OpenSSL 1.1.0
COPYRIGHT
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>.
3.0.1 2021-12-14 BN_MOD_MUL_RECIPROCAL(3ossl)
openssl 3.0.1 - Generated Tue Dec 21 08:31:40 CST 2021