Ultralightweight Cryptography for Low Cost Passive RFID Tags

Abstract

Radio Frequency IDentification (RFID) is one of the most promising identification schemes in the field of pervasive systems. Non-line of sight capability makes RFID systems more protuberant than its contended systems (such as barcode, magnetic tape etc.). RFID systems mainly consist of three main components: tag, reader and the backend database. A tag is a small electronic chip (transponder) implanted on an object which needs to be identified. A reader scans the tags, collects identification information and forwards this information towards the backend database (server) for the final verification. Security and privacy are the two major concerns of RFID based identification systems which are associated with the tag’s cost. On the basis of the tag’s cost and computational capabilities, the RFID tags can be classified into two types: high and low cost tags. Our research work focuses on low cost RFID tags. High cost tags are resourceful enough to support traditional cryptographic algorithms and primitives such as AES, hash functions, stream ciphers etc. for security. These conventional cryptographic algorithms and primitives have excessive power, memory and silicon (chip) area requirements; which are transcendent from the low cost tag’s computational capabilities. Hence, a new field ultralightweight cryptography has been introduced to ensure the security of low cost RFID tags in recent years. Ultralightweight cryptography avoids the use of costly operations and supports only simple T-functions and some special purpose ultralightweight primitives for the security. This research examines the security issues of low cost RFID systems and makes five contributions. First, we perform the security analysis of numerous Ultralightweight Mutual Authentication Protocols (UMAPs) and discuss the pitfalls in the design of these protocols. Secondly, we present a sophisticated security model to validate the security claims of the UMAPs and cryptanalyze four eminent UMAPs (EMAP, SASI, Yeh et al. and RAPP). We use Recursive Linear Cryptanalysis (RLC) on SASI protocol and quasi linear cryptanalysis on Yeh et al. to retrieve tag’s secret 𝐼𝐷. Further desynchronization and two Denial of Service (DoS) attacks on RAPP protocol have also been highlighted. Thirdly, we propose three new UMAPs (RCIA, SASI using Recursive Hash and KMAP) which are robust against all possible existing attacks. Moreover, a counter based methodology has also been assimilated with GOASSMER protocol and R2AP to avoid multiple DoS attacks and traceability attacks. Since the proper hardware implementation of such UMAPs has been long neglected, hence it is unclear that whether such protocols are practically compatible with low cost RFID tags having limited on-chip hardware compatibility or not. We therefore present an efficient hardware implementation of proposed UMAPs for EPC-C1G2 tags using both FPGA and ASIC design flows as our fourth contribution. The simulation and synthesis results of the proposed optimized hardware architecture show the compatibility of the proposed UMAPs with extremely low cost RFID tags. The low cost RFID tags don’t support conventional cryptographic primitives such as on-chip random number generators and conventional hash functions due to resource constraints. We propose two new primitives, Rot and Recursive Hash, to generate the Pseudorandom Numbers which result in Ultralightweight Pseudorandom Number Generators (UPRNGs). We analyze their performance analysis, statistical properties and the efficient hardware implementation to validate their practical feasibility with the low cost RFID tags.