Cryptanalysis of Multi-Server Authenticated Key Agreement Scheme Based   on Trust Computing Using Smart Cards and Biometrics
  Advancement in communication technology provides a scalable platform for various services where a remote user can access the server from anywhere without moving from its place. It has provided a unique opportunity for online services, such that the user need not physically present at the service center. These services adopt authentication and key agreement protocols to ensure authorized and secure access to resources. Most of the authentication schemes support single server environment where the user has to register with each server. If a user wishes to access multiple application servers, he requires to register with each of the servers. Although multi-server authentication schemes introduced a scalable platform such that a user can interact with any server using single registration. Recently, Chuang and Chen proposed an efficient multi-server authenticated key agreement scheme based on smart cards along with password and biometrics. This is a lightweight authentication scheme which requires the computation of only hash function. In this article, we present a brief review of Chuang and Chen's scheme. We analyze Chuang and Chen's scheme and identify that their scheme does not resist stolen smart card attack which causes the user's impersonation attack, server spoofing attack and man-in-the middle attack. Additionally, we show that their scheme has a weak key agreement protocol, which does not ensure forward secrecy. 
Dheerendra Mishra
cs.CR