An Improved Dynamic Certificateless Authenticated Asymmetric Group Key Agreement Protocol with Trusted KGC

Abstract

Asymmetric group key agreement allows a group of users to negotiate a common public encryption key, and each user only holds his own secret encryption key. Authenticated asymmetric group key agreement (AAGKA) protocol is a kind of AGKA protocols which can be secure against active attacks. Dynamic asymmetric group key agreement allows any member to join and leave at any point. This paper studies dynamic AAGKA in certificateless cryptography. We first pointed that Wei et al.’s dynamic certificateless AAGKA protocol suffers from a key compromise impersonation attack, and cannot provide secrecy or forward secrecy. We then proposed an improved dynamic certificateless AAGKA protocol. Security proofs show that our protocol can provide security attributes including secrecy, known-key security, key compromise impersonation resistance, forward security, non-repudiation, and privacy. Furthermore, the proposed protocol is still efficient.