=pod

=head1 NAME

SRP_Calc_server_key,
SRP_Calc_A,
SRP_Calc_B_ex,
SRP_Calc_B,
SRP_Calc_u_ex,
SRP_Calc_u,
SRP_Calc_x_ex,
SRP_Calc_x,
SRP_Calc_client_key_ex,
SRP_Calc_client_key
- SRP authentication primitives

=head1 SYNOPSIS

 #include <openssl/srp.h>

 /* server side .... */
 BIGNUM *SRP_Calc_server_key(const BIGNUM *A, const BIGNUM *v, const BIGNUM *u,
                             const BIGNUM *b, const BIGNUM *N);
 BIGNUM *SRP_Calc_B_ex(const BIGNUM *b, const BIGNUM *N, const BIGNUM *g,
                       const BIGNUM *v, OPENSSL_CTX *libctx, const char *propq);
 BIGNUM *SRP_Calc_B(const BIGNUM *b, const BIGNUM *N, const BIGNUM *g,
                   const BIGNUM *v);

 BIGNUM *SRP_Calc_u_ex(const BIGNUM *A, const BIGNUM *B, const BIGNUM *N,
                       OPENSSL_CTX *libctx, const char *propq);
 BIGNUM *SRP_Calc_u(const BIGNUM *A, const BIGNUM *B, const BIGNUM *N);

 /* client side .... */
 BIGNUM *SRP_Calc_client_key_ex(const BIGNUM *N, const BIGNUM *B, const BIGNUM *g,
                             const BIGNUM *x, const BIGNUM *a, const BIGNUM *u,
                             OPENSSL_CTX *libctx, const char *propq);
 BIGNUM *SRP_Calc_client_key(const BIGNUM *N, const BIGNUM *B, const BIGNUM *g,
                             const BIGNUM *x, const BIGNUM *a, const BIGNUM *u);
 BIGNUM *SRP_Calc_x_ex(const BIGNUM *s, const char *user, const char *pass,
                       OPENSSL_CTX *libctx, const char *propq);
 BIGNUM *SRP_Calc_x(const BIGNUM *s, const char *user, const char *pass);
 BIGNUM *SRP_Calc_A(const BIGNUM *a, const BIGNUM *N, const BIGNUM *g);

=head1 DESCRIPTION

The SRP functions described on this page are used to calculate various
parameters and keys used by SRP as defined in RFC2945. The server key and I<B>
and I<u> parameters are used on the server side and are calculated via
SRP_Calc_server_key(), SRP_Calc_B_ex(), SRP_Calc_B(), SRP_Calc_u_ex() and
SRP_Calc_u(). The client key and B<x> and B<A> parameters are used on the
client side and are calculated via the functions SRP_Calc_client_key_ex(),
SRP_Calc_client_key(), SRP_Calc_x_ex(), SRP_Calc_x() and SRP_Calc_A(). See
RFC2945 for a detailed description of their usage and the meaning of the various
BIGNUM parameters to these functions.

Most of these functions come in two forms. Those that take a I<libctx> and
I<propq> parameter, and those that don't. Any cryptogrpahic functions that
are fetched and used during the calculation use the provided I<libctx> and
I<propq>. See L<provider(7)/Fetching algorithms> for more details. The variants
that do not take a I<libctx> and I<propq> parameter use the default library
context and property query string. The SRP_Calc_server_key() and SRP_Calc_A()
functions do not have a form that takes I<libctx> or I<propq> parameters because
they do not need to fetch any cryptographic algorithms.

=head1 RETURN VALUES

All these functions return the calculated key or parameter, or NULL on error.

=head1 SEE ALSO

L<openssl-srp(1)>,
L<SRP_VBASE_new(3)>,
L<SRP_user_pwd_new(3)>

=head1 HISTORY

These functions were added in OpenSSL 1.0.1.

=head1 COPYRIGHT

Copyright 2020 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
L<https://www.openssl.org/source/license.html>.

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