openssl/doc/man3/RSA_size.pod

=pod

=head1 NAME

RSA_size, RSA_bits, RSA_security_bits - get RSA modulus size or security bits

=head1 SYNOPSIS

 #include <openssl/rsa.h>

 int RSA_bits(const RSA *rsa);

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 RSA_size(const RSA *rsa);

 int RSA_security_bits(const RSA *rsa);

=head1 DESCRIPTION

RSA_bits() returns the number of significant bits.

B<rsa> and B<rsa-E<gt>n> must not be B<NULL>.

The remaining functions described on this page are deprecated.
Applications should instead use L<EVP_PKEY_get_size(3)>, L<EVP_PKEY_get_bits(3)>
and L<EVP_PKEY_get_security_bits(3)>.

RSA_size() returns the RSA modulus size in bytes. It can be used to
determine how much memory must be allocated for an RSA encrypted
value.

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

=head1 RETURN VALUES

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

RSA_size() returns the size of modulus in bytes.

RSA_security_bits() returns the number of security bits.

=head1 SEE ALSO

L<BN_num_bits(3)>

=head1 HISTORY

The RSA_size() and RSA_security_bits() functions were deprecated in OpenSSL 3.0.

The RSA_bits() function was added in OpenSSL 1.1.0.

=head1 COPYRIGHT

Copyright 2000-2021 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