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=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_size(const DH *dh);

 int DH_bits(const DH *dh);

 int DH_security_bits(const DH *dh);

=head1 DESCRIPTION

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_bits() returns the number of significant bits.

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

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_size() returns the prime size of Diffie-Hellman in bytes.

DH_bits() returns the number of bits in the key.

DH_security_bits() returns the number of security bits.

=head1 SEE ALSO

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

=head1 HISTORY

The DH_bits() function was added in OpenSSL 1.1.0.

=head1 COPYRIGHT

Copyright 2000-2018 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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