## 1 Introduction  
Mobile adhoc network (MANET) is a multi-hop network consisting of only nodes without infrastructure. It has been used when network construction is needed quickly in special situations. For example, it may be implemented to deliver packets to soldiers on the battlefield, conference participants, and vehicles on the road. Therefore, all nodes participating in the network must act as routers [1]. The limited number of nodes and the limited bandwidth of the wireless medium should reduce power consumption and transmission overhead. In addition, efficient routing is very important because all nodes act as hosts and routers and move quickly in most cases. MANET requires efficient group communication protocols such as multicast due to its limited bandwidth, dynamic topology by the movement of nodes, and high transmit receive error rates [2, 3]. Multicasting is an ideal communication way to efficiently support various applications that require collaboration between nodes. Therefore, it supports applications that simultaneously transmit data to the host. Since the nodes constituting the multicast group may move, any rapid topology may change at unpredictable times. Therefore, tree reorganization methods and membership information logging techniques should be as simple as possible to reduce channel overhead. Limited power, limited bandwidth, and mobile hosts make multicast protocol design difficult [4]. In MANET, multicast is divided into IP multicast at the network layer and overlay multicast at the application layer. For multicast at the network layer, all nodes should be recognized as multicast services, and nodes that do not participate in multicast should be managed. In addition, if nodes move frequently, the overhead of maintaining the state of the nodes increases and multicast efficiency decreases [5]. Overlay multicasting creates a virtual multicast topology and services. Although it has an advantage independently for a routing protocol, it has the disadvantage of being difficult to transmit data using an optimal route. If malicious nodes attack and prevent data transmission, the multicast service becomes impossible. Therefore, it is necessary to study virtual topology configuration and security for efficient data transmission [6]. In this paper, we proposed a secure multicast routing model to provide node management efficiency and high data reliability. This paper applies a region-based routing approach for optimal path and member node management. Region-based routing improves overall network performance by distributing the load effectively. In order to apply the ZSM technique, nodes participating in the network were divided into general nodes, member nodes, group management nodes, and authentication nodes according to each role. A group management node is selected for each zone in order to manage member nodes participating in multicast. It stores and manages a variety of information about the member node in the group node table and periodically exchanges the information of the group node table with the neighbor group management node. At this point, encryption is performed using the group key issued by the authentication node, and the member node is responsible for issuing the member key used for encryption when transmitting data. The optimal transmission route can be maintained when data are transmitted by managing the state information of member nodes. The authentication node becomes the member node having the most nodes among the group management nodes. It is responsible for issuing the group key. The group key is used to encrypt the data received by the member node from the group management node. The ZSM technique in this paper consists of two steps of encryption for data transmission. Through this process, it was possible to block the participation of malicious nodes in multicast and be stronger against data forgery and eavesdropping attacks.