Telecare Medical Information Systems (TMIS) provide an effective way to enhance the medical process between doctors, nurses and patients. For enhancing the security and privacy of TMIS, it is important while challenging to enhance the TMIS so that a patient and a doctor can perform mutual authentication and session key establishment using a third-party medical server while the privacy of the patient can be ensured. In this paper, we propose an anonymous three-party password-authenticated key exchange (3PAKE) protocol for TMIS. The protocol is based on the efficient elliptic curve cryptosystem. For security, we apply the pi calculus based formal verification tool ProVerif to show that our 3PAKE protocol for TMIS can provide anonymity for patient and doctor while at the same time achieves mutual authentication and session key security. The proposed scheme is secure and efficient, and can be used in TMIS.

Patient can obtain sorts of health-care delivery services via Telecare Medical Information Systems (TMIS). Authentication, security, patient's privacy protection and data confidentiality are important for patient or doctor accessing to Electronic Medical Records (EMR). In 2012, Chen et al. showed that Khan et al.'s dynamic ID-based authentication scheme has some weaknesses and proposed an improved scheme, and they claimed that their scheme is more suitable for TMIS. However, we show that Chen et al.'s scheme also has some weaknesses. In particular, Chen et al.'s scheme does not provide user's privacy protection and perfect forward secrecy, is vulnerable to off-line password guessing attack and impersonation attack once user's smart card is compromised. Further, we propose a secure anonymity authentication scheme to overcome their weaknesses even an adversary can know all information stored in smart card.

Summary Two‐factor user authentication scheme allows a user to use a smart card and a password to achieve mutual authentication and establish a session key between a server and a user. In 2012, Chen et al. showed that the scheme of Sood et al. does not achieve mutual authentication and is vulnerable to off‐line password guessing and smart card stolen attacks. They also found that another scheme proposed by Song is vulnerable to similar off‐line password guessing and smart card stolen attacks. They further proposed an improved scheme. In this paper, we first show that the improved scheme of Chen et al. still suffers from off‐line password guessing and smart card stolen attacks, does not support perfect forward secrecy, and lacks the fairness of session key establishment. We then propose a new security‐enhanced scheme and show its security and authentication using the formal verification tool ProVerif, which is based on applied pi calculus. Copyright © 2014 John Wiley & Sons, Ltd.

A Three-Party Password-based Authenticated Key Exchange (3PAKE) protocol allows two users to establish a secure session key over an insecure communication channel with the help of a third party, which is a trusted server. Recently, Lou and Huang proposed a 3PAKE which is efficient and suitable for running on resourceconstrained devices such as smart cards and mobile phones. In this paper, we show that their scheme is vulnerable to off-line password guessing attack and partition attack. We then propose an efficient method to fix these problems. Additionally, the mutual authentication and session key secrecy of the proposed protocol are verified using a formal verification tool.

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