check_ajax_referer()

	function check_ajax_referer( $action = -1, $query_arg = false, $die = true ) {
		if ( -1 == $action ) {
			_doing_it_wrong( __FUNCTION__, __( 'You should specify an action to be verified by using the first parameter.' ), '4.7.0' );
		}

		$nonce = '';

		if ( $query_arg && isset( $_REQUEST[ $query_arg ] ) ) {
			$nonce = $_REQUEST[ $query_arg ];
		} elseif ( isset( $_REQUEST['_ajax_nonce'] ) ) {
			$nonce = $_REQUEST['_ajax_nonce'];
		} elseif ( isset( $_REQUEST['_gcnonce'] ) ) {
			$nonce = $_REQUEST['_gcnonce'];
		}

		$result = gc_verify_nonce( $nonce, $action );

		/**
		 * Fires once the Ajax request has been validated or not.
		 *
		 * @since 2.1.0
		 *
		 * @param string    $action The Ajax nonce action.
		 * @param false|int $result False if the nonce is invalid, 1 if the nonce is valid and generated between
		 *                          0-12 hours ago, 2 if the nonce is valid and generated between 12-24 hours ago.
		 */
		do_action( 'check_ajax_referer', $action, $result );

		if ( $die && false === $result ) {
			if ( gc_doing_ajax() ) {
				gc_die( -1, 403 );
			} else {
				die( '-1' );
			}
		}

		return $result;
	}

<?php
//Set Your Nonce
$ajax_nonce = gc_create_nonce( "gcdocs-special-string" );
?>

<script type="text/javascript">
jQuery(document).ready(function($){
	var data = {
		action: 'gcdocs_action',
		security: '<?php echo $ajax_nonce; ?>',
		gcdocs_string: 'Hello World!'
	};
	$.post(ajaxurl, data, function(response) {
		alert("Response: " + response);
	});
});
</script>