=pod =head1 NAME BN_mod_mul_reciprocal, BN_div_recp, BN_RECP_CTX_new, BN_RECP_CTX_free, BN_RECP_CTX_set - modular multiplication using reciprocal =head1 SYNOPSIS #include 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, BIGNUM *a, BN_RECP_CTX *recp, BN_CTX *ctx); int BN_mod_mul_reciprocal(BIGNUM *r, BIGNUM *a, BIGNUM *b, BN_RECP_CTX *recp, BN_CTX *ctx); =head1 DESCRIPTION BN_mod_mul_reciprocal() can be used to perform an efficient L operation when the operation will be performed repeatedly with the same modulus. It computes B=(B*B)%B using B=1/B, which is set as described below. B is a previously allocated B used for temporary variables. BN_RECP_CTX_new() allocates and initializes a B structure. BN_RECP_CTX_free() frees the components of the B, and, if it was created by BN_RECP_CTX_new(), also the structure itself. If B is NULL, nothing is done. BN_RECP_CTX_set() stores B in B and sets it up for computing 1/B and shifting it left by BN_num_bits(B)+1 to make it an integer. The result and the number of bits it was shifted left will later be stored in B. BN_div_recp() divides B by B using B. It places the quotient in B and the remainder in B. The B structure cannot be shared between threads. =head1 RETURN VALUES BN_RECP_CTX_new() returns the newly allocated B, 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 L. =head1 SEE ALSO L, L, L =head1 HISTORY BN_RECP_CTX_init() was removed in OpenSSL 1.1.0 =head1 COPYRIGHT Copyright 2000-2017 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 L. =cut