Abstract
The denial-of-service attack, a malicious client executes a key agreement protocol simultaneously many times to exhaust the server's memory or computing resource and to interfere the honest client connecting with the server. It is a serious problem in the key agreement protocol. A key agreement protocol which resists to the storage-exhaustion and the CPU-exhaustion attack was firstly proposed by Hiros-Matsuura. However, their protocol is not efficient enough during the weak key validation. Our proposed protocol modifies the weak key validation and avoids the unnecessary heavy computation to enhance the resistance of the denial-of-service attack. The most important contributions of our protocol are not only efficiently to resist CPU-exhaustion and memory-exhaustion attacks but also prevent bandwidth consumption.