On the group key transfer protocol using secret sharing

Recently, some group key transfer protocols are proposed using Shamir’s secret sharing, which are claimed to be secure to resist the insider attack and the outsider attack. In fact, some claims are not really true. In this paper, we review the recently proposed protocol by Yuan et al. and the cryptanalysis presented by Olimid, then give the improved version to guarantee the security and low communication cost. Especially, we analyze why the insider adversary can deduce other’s long term secret, and give the solution to avoid the insider attack.