Efficient delegation-based authentication protocol with strong mobile privacy

In 2008, Tang and Wu designed a one-time alias mechanism for protecting the mobile privacy of a user. Recently, Youn and Lim proposed an improved delegation-based authentication protocol to provide private roaming service. In this article, we show that a link between requests may disclose information about the mobile privacy of a sender, and that the aliases of a user fail to achieve the unlinkability in Tan-Wu's scheme. We remedy this situation by suggesting an enhanced protocol that utilizes a pseudorandom function. Compared to Youn-Lim's protocol, our design is more efficient than theirs.