Efficient authenticated key agreement protocols resistant to a denial-of-service attack

Malicious intruders may launch as many invalid requests as possible without establishing a server connection to bring server service to a standstill. This is called a denial-of-service (DoS) or distributed DoS (DDoS) attack. Until now, there has been no complete solution to resisting a DoS/DDoS attack. Therefore, it is an important network security issue to reduce the impact of a DoS/DDoS attack. A resourceexhaustion attack on a server is one kind of denial-of-service attack. In this article we address the resource-exhaustion problem in authentication and key agreement protocols. The resource-exhaustion attack consists of both the CPU-exhaustion attack and the storage-exhaustion attack. In 2001, Hirose and Matsuura proposed an authenticated key agreement protocol (AKAP) that was the first protocol simultaneously resistant to both the CPU-exhaustion attack and the storage-exhaustion attack. However, their protocol is time-consuming for legal users in order to withstand the DoS attack. Therefore, in this paper, we propose a slight modification to the Hirose–Matsuura protocol to reduce the computation cost. Both the Hirose–Matsuura and the modified protocols provide implicit key confirmation. Also, we propose another authenticated key agreement protocol with explicit key confirmation. The new protocol requires less computation cost. Because DoS/DDoS attacks come in a variety of forms, the proposed protocols cannot fully disallow a DoS/DDoS attack. However, they reduce the effect of such an attack and thus make it more difficult for the attack to succeed. Copyright © 2005 John Wiley & Sons, Ltd.