ON THE SECURITY OF A PRIVACY-AWARE AUTHENTICATION SCHEME FOR DISTRIBUTED MOBILE CLOUD COMPUTING SERVICES
Recently, Tsai and Lo proposed a privacy aware authentication scheme for distributed mobile cloud computing services. It is claimed that the scheme achieves mutual authentication and withstands all major security threats. However, we first identify that their scheme fails to achieve
Mutual authentication, because it is vulnerable to the service provider impersonation attack. Beside this major defect, it also suffers from some minor design flaws, including the problem of biometrics misuse, wrong password, and fingerprint login, no user revocation facility when the smart card is lost/stolen. Some suggestions are provided to avoid these design flaws in the future design of authentication schemes.
Index Terms—Authentication, bilinear pairing, mobile cloud computing, security, user anonymity, user intractability.
Since wireless networks underlying mobile cloud computing are vulnerable to a series of attacks, such as eavesdropping, replay, forgery, interception, and denial of service attacks, mutual authentication between the user and cloud service provider is indispensable to prevent illegal service access and defend the potential security attacks over the insecure networks. Additionally,
as identity threats, such as identity masquerade and identity tracing, have become common attacks in wireless networks, there is a growing demand to protect user identity privacy. Furthermore, a mobile user generally accesses different types of mobile Manuscript received June 22, 2015; revised November 01, 2015 and April 16, 2016; accepted May 20, 2016. This work was supported in part by National Science Foundation of China (61202389, U1405255, 61309016, 61372075, U1536202), in part by Natural Science Basic Research Plan in Shaanxi Province of China (2016JM6005), in part by Fundamental Research Funds for the Central Universities (JB161501), in part by the Priority Academic Program Development of Jiangsu Higher Education Institutions and Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, it is essential to design a privacy aware authentication scheme which enables users to access various services from distinct service providers by using only one single private key or password. Apart from these issues, mobile devices are relatively limited in computing capability and power compared with desktop computers, the scheme should be efficient in terms of computing. More desirably, the trusted third party, involved in user registration and service provider registration, is not required to participate in each user authentication session. Most authentication protocols, which are designed for single server environment, are not suitable for distributed services environment in which multiple servers offer a plethora of services.
To the best of our knowledge, there is no direct approach to remedy the major defect of service provider impersonation attack. To counteract this vulnerability, the scheme needs radical improvements, which deserves a full paper. Thus, we leave it as our future work. Regarding these minor design flaws discussed in the previous section, we provide some suggestions to avoid them in the future design of three-factor authentication schemes. 1) A possible countermeasure to misuse of biometrics is to employ bio-cryptosystem, such as fuzzy extractor, instead of directly applying hash function to biometrics. The basic concept of fuzzy extractor is to generate the biometric key, i.e., a pair of strings (P,R), from the biometrics, where P is the help string and R is the secret key. R can be recovered if P and a close enough biometrics are provided. The error tolerance of fuzzy extractor is enabled by error correcting techniques. In fuzzy vault, a user generates a secret key and encrypt it by using his/her biometric template. The secret key can be recovered by providing the encrypted data and the corresponding biometrics. 2) It is desired that an authentication test is in place to verify the correctness of Ui ’ credentials, i.e., IDi, PWi , and fi before sending the message (K2, C1 ). However, there is a tradeoff between fulfilling authentication test and resisting offline dictionary attack. A possible fix is to employ the concept of fuzzy verifier proposed. On one hand, it can be used to provide timely wrong password and fingerprint detection when login. On the other hand, the adversary has to perform online guessing to determine the correct password from as high as 212 candidates, which can be relatively easily detected and thwarted by the server by using rate limiting and/or lockout policy. 3) To facilitate revocation, the SCG maintains the identity information in its database, based on which the invalid smart card will be detected .
We have analyzed an efficient and provably secure authentication scheme for mobile computing services by Tsai and Lo. Although their scheme is equipped with a claimed proof of provable security, we have pointed out the scheme fails to achieve mutual authentication by demonstrating its vulnerability to the service provider impersonation attack. Besides this major defect, it also suffers from some minor design flaws, including the misuse of biometrics, wrong password and fingerprint login, and no user revocation facility when the smart card is lost/stolen.We have provided some suggestions to avoid these design flaws in the future design of authentication schemes combining passwords, smart cards, and biometrics. A natural direction for further study is to design a secure and efficient authentication scheme for distributed mobile cloud services
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