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=head1 NAME

BN_security_bits - returns bits of security based on given numbers

=head1 SYNOPSIS

 #include <openssl/bn.h>

 int BN_security_bits(int L, int N);

=head1 DESCRIPTION

BN_security_bits() returns the number of bits of security provided by a
specific algorithm and a particular key size. The bits of security is
defined in NIST SP800-57. Currently, BN_security_bits() support two types
of asymmetric algorithms: the FFC (Finite Field Cryptography) and IFC
(Integer Factorization Cryptography). For FFC, e.g., DSA and DH, both
parameters B<L> and B<N> are used to decide the bits of security, where
B<L> is the size of the public key and B<N> is the size of the private
key. For IFC, e.g., RSA, only B<L> is used and it's commonly considered
to be the key size (modulus).

=head1 RETURN VALUES

Number of security bits.

=head1 NOTES

ECC (Elliptic Curve Cryptography) is not covered by the BN_security_bits()
function. The symmetric algorithms are not covered neither.

=head1 SEE ALSO

L<DH_security_bits(3)>, L<DSA_security_bits(3)>, L<RSA_security_bits(3)>

=head1 HISTORY

The BN_security_bits() function was added in OpenSSL 1.1.0.

=head1 COPYRIGHT

Copyright 2017-2019 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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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