=pod
=head1 NAME
BN_mod_mul_reciprocal, BN_div_recp, BN_RECP_CTX_new, BN_RECP_CTX_init,
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_init(BN_RECP_CTX *recp);
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_init() initializes an existing uninitialized B.
BN_RECP_CTX_free() frees the components of the B, and, if it
was created by BN_RECP_CTX_new(), also the structure itself.
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 is defined as follows:
typedef struct bn_recp_ctx_st
{
BIGNUM N; /* the divisor */
BIGNUM Nr; /* the reciprocal */
int num_bits;
int shift;
int flags;
} BN_RECP_CTX;
It cannot be shared between threads.
=head1 RETURN VALUES
BN_RECP_CTX_new() returns the newly allocated B, and NULL
on error.
BN_RECP_CTX_init() and BN_RECP_CTX_free() have no return values.
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,
L
=head1 HISTORY
B was added in SSLeay 0.9.0. Before that, the function
BN_reciprocal() was used instead, and the BN_mod_mul_reciprocal()
arguments were different.
=cut
**