=pod

=head1 NAME

RSA_check_key - validate private RSA keys

=head1 SYNOPSIS

 #include <openssl/rsa.h>

 int RSA_check_key(RSA *rsa);

=head1 DESCRIPTION

This function validates RSA keys. It checks that B<p> and B<q> are
in fact prime, and that B<n = p*q>.

It also checks that B<d*e = 1 mod (p-1*q-1)>,
and that B<dmp1>, B<dmq1> and B<iqmp> are set correctly or are B<NULL>.

As such, this function can not be used with any arbitrary RSA key object,
even if it is otherwise fit for regular RSA operation. See B<NOTES> for more
information.

=head1 RETURN VALUE

RSA_check_key() returns 1 if B<rsa> is a valid RSA key, and 0 otherwise.
-1 is returned if an error occurs while checking the key.

If the key is invalid or an error occurred, the reason code can be
obtained using L<ERR_get_error(3)|ERR_get_error(3)>.

=head1 NOTES

This function does not work on RSA public keys that have only the modulus
and public exponent elements populated. It performs integrity checks on all
the RSA key material, so the RSA key structure must contain all the private
key data too.

=head1 SEE ALSO

L<rsa(3)|rsa(3)>, L<ERR_get_error(3)|ERR_get_error(3)>

=head1 HISTORY

RSA_check_key() appeared in OpenSSL 0.9.4.

=cut
