public static function keyIsValid( $key )
	{
		$key = C4gActivationkeyModel::findOneBy( 'activationkey', hash('sha256', $key) );
		// the key exists, is not already claimed and is not expired
		return (!empty( $key ) && empty( $key->used_by ) && ($key->expiration_date == 0 || $key->expiration_date > time()));
	}