Provably secure authenticated key agreement scheme for distributed mobile cloud computing services

With the rapid development of mobile cloud computing, the security becomes a crucial part of communication systems in a distributed mobile cloud computing environment. Recently, in 2015, Tsai and Lo proposed a privacy-aware authentication scheme for distributed mobile cloud computing services. In this paper, we first analyze the Tsai-Lo's scheme and show that their scheme is vulnerable to server impersonation attack, and thus, their scheme fails to achieve the secure mutual authentication. In addition, we also show that Tsai-Lo's scheme does not provide the session-key security (SK-security) and strong user credentials' privacy when ephemeral secret is unexpectedly revealed to the adversary. In order to withstand these security pitfalls found in Tsai-Lo's scheme, we propose a provably secure authentication scheme for distributed mobile cloud computing services. Through the rigorous security analysis, we show that our scheme achieves SK-security and strong credentials' privacy and prevents all well-known attacks including the impersonation attack and ephemeral secrets leakage attack. Furthermore, we simulate our scheme for the formal security analysis using the widely-accepted AVISPA (Automated Validation of Internet Security Protocols and Applications) tool, and show that our scheme is secure against passive and active attacks including the replay and man-in-the-middle attacks. More security functionalities along with reduced computational costs for the mobile users make our scheme more appropriate for the practical applications as compared to Tsai-Lo's scheme and other related schemes. Finally, to demonstrate the practicality of the scheme, we evaluate the proposed scheme using the broadly-accepted NS-2 network simulator.