=pod

=head1 NAME

EVP_PKEY_get_default_digest_nid - get default signature digest

=head1 SYNOPSIS

 #include <openssl/evp.h>
 int EVP_PKEY_get_default_digest_nid(EVP_PKEY *pkey, int *pnid);

=head1 DESCRIPTION

The EVP_PKEY_get_default_digest_nid() function sets B<pnid> to the default
message digest NID for the public key signature operations associated with key
B<pkey>. Note that some signature algorithms (i.e. Ed25519 and Ed448) do not use
a digest during signing. In this case B<pnid> will be set to NID_undef.

=head1 NOTES

For all current standard OpenSSL public key algorithms SHA256 is returned.

=head1 RETURN VALUES

The EVP_PKEY_get_default_digest_nid() function returns 1 if the message digest
is advisory (that is other digests can be used) and 2 if it is mandatory (other
digests can not be used).  It returns 0 or a negative value for failure. In
particular a return value of -2 indicates the operation is not supported by the
public key algorithm.

=head1 SEE ALSO

L<EVP_PKEY_CTX_new(3)>,
L<EVP_PKEY_sign(3)>,
L<EVP_PKEY_supports_digest_nid(3)>,
L<EVP_PKEY_verify(3)>,
L<EVP_PKEY_verify_recover(3)>,

=head1 HISTORY

This function was first added to OpenSSL 1.0.0.

=head1 COPYRIGHT

Copyright 2006-2018 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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