Abstract: With the rapid growth of Internet applications, the architecture of server providing resources to be accessed over the network often consists of many different servers. Authentication and key agreement protocol play an important role to authenticate remote users for multi-server architecture. In recent years, several authentication and key agreement protocols for multi-server architecture have been developed. Single registration is the most important feature in a multi-server architecture which may help users take desired services without repeating registration to each service provider. Employing a dynamic ID for each login may efficiently preserve privacy. Recently, Chuang et al. presented an anonymous multi-server authenticated key agreement scheme based on trust computing using smart cards and biometrics. They claimed that their protocol not only supported multi-server environments but also achieved many security requirements. A cryptanalysis on Chuang et al.’s scheme shows that their scheme cannot provide the anonymity and is vulnerable to server masquerade attack and smart card loss attack. To overcome these security flaws, an improved protocol is proposed by choosing different secret parameters for each application server. This protocol can be proved to be secure against server masquerade attack, smart card loss attack, impersonation attack, eavesdropping attack, replay attack and so on. Besides, the improved protocol maintains the feature of simple operation.

Key words: authentication, key agreement, anonymous, multi-server, biometrics