The Computer Journal Advance Access originally published online on May 13, 2005
The Computer Journal 2005 48(4):480-487; doi:10.1093/comjnl/bxh111
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A Robust Multi-Party Key Agreement Protocol Resistant to Malicious Participants
Department of Mathematics, National Changhua University of Education, Jin-De Campus, Chang-Hua, Taiwan 500, R.O.C.
By its very nature, a non-authenticated multi-party key agreement protocol cannot provide participant and message authentication, so it must rely on an authenticated network channel. This paper presents the inability of two famous multi-party key agreement protocols to withstand malicious participant attacks, even though their protocols are based on the authenticated network channel. This attack involves a malicious participant disrupting the multi-party key agreement among honest participants. In this case, other honest participants do not correctly agree on a common key. Obviously, the malicious participant cannot obtain the common key either, and the communication confidentiality among participants is not breached. However, in some emergency situations or applications, a multi-party key agreement protocol design that is resistant to malicious participants is useful. Therefore, in this paper, a non-authenticated multi-party key agreement protocol resistant to malicious participants is proposed. The proposed robust protocol requires constant rounds to establish a common key. Each participant broadcasts a constant number of messages. Under the assumption of the Decision Diffie–Hellman problem and the random oracle model, we will show that the proposed protocol is provably secure against passive adversaries and malicious participants.
Received 29 July 2004. revised 25 April 2005.