Cryptanalysis of a Group Key Transfer Protocol Based on Secret Sharing: Generalization and Countermeasures
Group key distribution protocol is a mechanism in which a group key is generated and distributed by KGC to a set of communicating parties in a group. This group key generally ensures secure communication among communicating parties in an unsecure channel. Harn and Lin protocol is one such. It is based on Shamir’s secret sharing scheme. Nam et al. exposed the vulnerability in Harn and Lin protocol through their replay attack and proposed a countermeasure using nonce mechanism. In this paper, we are generalizing the replay attack proposed by Nam et al. and proposing an alternative countermeasure without using nonce mechanism. Novelty of our countermeasure is that KGC is not required to detect replay messages and hence each user doesn’t need to compute authentication message as in Nam et al. Proposed countermeasure thereby brings down the computational complexity of the scheme.