Abstract The availability of the Web service has been exposed to several threats such as distributed denial‐of‐service attack, which is not an unfamiliar terminology anymore. Sustaining availability against various attacks becomes the critical issue for high‐profile Web sites. In this paper, we propose a novel architecture providing Web service among client, called client cloud Web service, by utilizing resources of clients to enhance the availability. Client cloud Web service can be easily integrated into the current Internet protocol suite by providing a transparent layer in the middle of Hypertext Transfer Protocol layer and Transmission Control Protocol/Internet Protocol layer. It is shown by simulations that the proposed architecture can efficiently reduce the traffic when both the size of Web items and the number of requests from clients increase. Copyright © 2012 John Wiley & Sons, Ltd.

Secure authentication in roaming services is being designed to allow legal users to get access to wireless network services when they are away from their home location. Recently, to protect the location privacy of users, there have been researches on anonymous authentication. In particular, anonymous authentication without the participation of home servers has attracted considerable interest owing to its influence on the communication efficiency. Unfortunately, the previously proposed anonymous authentication schemes have serious practical shortcomings, such as high communication and computation costs and huge revocation lists. In this paper, we propose a novel three-round anonymous roaming protocol that does not require the participation of home servers. The proposed protocol uses a pseudo-identity-based signcryption scheme to perform efficient revocation with a short revocation list and efficient authentication. The use of a signcryption algorithm minimizes the number of pseudo-identities stored in a Subscriber Identification Module (SIM) card with limited storage capacity. The authentication efficiency is also higher than that of existing protocols. The proposed protocol is formally proved in the Canetti-Krawczyk (CK) model.