A Lightweight Pseudonym Authentication and Key Agreement Protocol for Multi-medical Server Architecture in TMIS

Telecare Medical Information System (TMIS) helps the patients to gain the health monitoring information at home and access medical services over the mobile Internet. In 2015, Das et al proposed a secure and robust user AKA scheme for hierarchical multi- medical server environment in TMIS, referred to as DAKA protocol, and claimed that their protocol is against all possible attacks. In this paper, we first analyze and show DAKA protocol is vulnerable to internal attacks, impersonation attacks and stolen smart card attack. Furthermore, DAKA protocol also cannot provide confidentiality. We then propose a lightweight pseudonym AKA protocol for multi- medical server architecture in TMIS (short for PAKA). Our PAKA protocol not only keeps good security features declared by DAKA protocol, but also truly provides patient's anonymity by using pseudonym to protect sensitive information from illegal interception. Besides, our PAKA protocol can realize authentication and key agreement with energy- saving, extremely low computation cost, communication cost and fewer storage resources in smart card, medical servers and physical servers. What's more, the PAKA protocol is proved secure against known possible attacks by using Burrows- Abadi- Needham (BAN) logic. As a result, these features make PAKA protocol is very suitable for computation- limited mobile device.