protected function _getKey( $sKeyType )
    {
        $sSettingName = (string) $sKeyType;
        $sSettingName .= 'Key';

        if ( $this->isSandboxMode() ) {
            $sSettingName .= 'Test';
        }

        $sEncodedKey = (string) $this->getSetting( $sSettingName );

        return !empty( $sEncodedKey ) ? base64_decode( $sEncodedKey ) : '';
    }