private function configureSslValidation()
    {
        // set SSL validation for the CAS server
        if ($this->config['cas_validation'] == 'ca' || $this->config['cas_validation'] == 'self')
        {
            phpCAS::setCasServerCACert($this->config['cas_cert']);
        }
        else
        {
            phpCAS::setNoCasServerValidation();
        }
    }