As one of the most well-studied cohesive subgraph models, the k-core is widely used to find graph nodes that are “central” or “important” in many applications, such as biological networks, social networks, ecological networks, and financial networks. For distributed networks, e.g., Decentralized Online Social Networks (DOSNs) such that each vertex is a client as a single computing unit, the distributed k-core decomposition algorithms are already proposed. However, current distributed approaches fail to adequately protect privacy and security. In this work, we are the first to propose the secure version of the distributed k-core decomposition.