BN_mod_mul_reciprocal, BN_div_recp, BN_RECP_CTX_new, BN_RECP_CTX_free,
BN_RECP_CTX_set - modular multiplication using reciprocal
#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);
BN_mod_mul_reciprocal() 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.
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).
ERR_get_error(3),
BN_add(3),
BN_CTX_new(3)
BN_RECP_CTX_init() was removed in OpenSSL 1.1.0
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>.