Scalability and Security Conflict for RFID Authentication Protocols

RFID technology continues to flourish as an inherent part of virtually every ubiquitous environment. However, it became clear that the public—implying the industry—seriously needs mechanisms emerging the security and privacy issues for increasing RFID applications. As the nodes of RFID systems mostly suffer from low computational power and small memory size, various attempts which propose to implement the existing security primitives and protocols, have ignored the realm of the cost limitations and failed. In this study, two recently proposed protocols—SSM and LRMAP—claiming to meet the standard privacy and security requirements are analyzed. The design of both protocols based on defining states where the server authenticates the tag in constant time in a more frequent normal state and needs a linear search in a rare abnormal states. Although both protocols claim to provide untraceability criteria in their design objectives, we outline a generic attack that both protocols failed to fulfill this claim. Moreover, we showed that the SSM protocol is vulnerable to a desynchronization attack which prevents a server from authenticating a legitimate tag. Resultantly, we conclude that defining computationally unbalanced tag states yields to a security/scalability conflict for RFID authentication protocols.