In this paper, the authors study about location based key management scheme in wireless mission-critical networks. A challenge of the key distribution scheme is to use small memory size to establish secure communication among a large number of nodes and achieve good resilience. In this paper, they present a new paradigm of public key management scheme based on combinatorial design where nodes combine more than one key to encrypt and decrypt every message. Here key allocation scheme guarantees that a set of keys held by one user is not a subset of keys held by any other user. It is challenging to design a self-constrained key management scheme in current wireless ad hoc networks.