=pod

=head1 NAME

EVP_PKEY_is_a, EVP_PKEY_can_sign
- key type and capabilities functions

=head1 SYNOPSIS

 #include <openssl/evp.h>

 int EVP_PKEY_is_a(const EVP_PKEY *pkey, const char *name);
 int EVP_PKEY_can_sign(const EVP_PKEY *pkey);

=head1 DESCRIPTION

EVP_PKEY_is_a() checks if the key type of I<pkey> is I<name>.

EVP_PKEY_can_sign() checks if the functionality for the key type of
I<pkey> supports signing.  No other check is done, such as whether
I<pkey> contains a private key.

=head1 RETURN VALUES

EVP_PKEY_is_a() returns 1 if I<pkey> has the key type I<name>,
otherwise 0.

EVP_PKEY_can_sign() returns 1 if the I<pkey> key type functionality
supports signing, otherwise 0.

=head1 EXAMPLES

=head2 EVP_PKEY_is_a()

The loaded providers and what key types they support will ultimately
determine what I<name> is possible to use with EVP_PKEY_is_a().  We do know
that the default provider supports RSA, DH, DSA and EC keys, so we can use
this as an crude example:

 #include <openssl/evp.h>

 ...
     /* |pkey| is an EVP_PKEY* */
     if (EVP_PKEY_is_a(pkey, "RSA")) {
         BIGNUM *modulus = NULL;
         if (EVP_PKEY_get_bn_param(pkey, "n", &modulus))
             /* do whatever with the modulus */
         BN_free(modulus);
     }

=head2 EVP_PKEY_can_sign()

 #include <openssl/evp.h>

 ...
     /* |pkey| is an EVP_PKEY* */
     if (!EVP_PKEY_can_sign(pkey)) {
         fprintf(stderr, "Not a signing key!");
         exit(1);
     }
     /* Sign something... */

=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>.

=cut