openssl/doc/man3/DH_size.pod

=pod

=head1 NAME

DH_size, DH_bits, DH_security_bits - get Diffie-Hellman prime size and
security bits

=head1 SYNOPSIS

 #include <openssl/dh.h>

 int DH_bits(const DH *dh);

Deprecated since OpenSSL 3.0, can be hidden entirely by defining
B<OPENSSL_API_COMPAT> with a suitable version value, see
L<openssl_user_macros(7)>:

 int DH_size(const DH *dh);

 int DH_security_bits(const DH *dh);

=head1 DESCRIPTION

DH_bits() returns the number of significant bits.

B<dh> and B<dh-E<gt>p> must not be B<NULL>.

The remaining functions described on this page are deprecated.
Applications should instead use L<EVP_PKEY_security_bits(3)> and
L<EVP_PKEY_size(3)>.

DH_size() returns the Diffie-Hellman prime size in bytes. It can be used
to determine how much memory must be allocated for the shared secret
computed by L<DH_compute_key(3)>.

DH_security_bits() returns the number of security bits of the given B<dh>
key. See L<BN_security_bits(3)>.

=head1 RETURN VALUES

DH_bits() returns the number of bits in the key, or -1 if
B<dh> doesn't hold any key parameters.

DH_size() returns the prime size of Diffie-Hellman in bytes, or -1 if
B<dh> doesn't hold any key parameters.

DH_security_bits() returns the number of security bits, or -1 if
B<dh> doesn't hold any key parameters.

=head1 SEE ALSO

L<EVP_PKEY_bits(3)>,
L<DH_new(3)>, L<DH_generate_key(3)>,
L<BN_num_bits(3)>

=head1 HISTORY

The DH_size() and DH_security_bits() functions were deprecated in OpenSSL 3.0.

The DH_bits() function was added in OpenSSL 1.1.0.

=head1 COPYRIGHT

Copyright 2000-2020 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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