PhD defence - Gangqiang Yang

Thursday, January 5, 2017 9:30 am - 9:30 am EST (GMT -05:00)


Gangqiang Yang


Optimized Hardware Implementations of Lightweight Cryptography


Guang Gong and Mark Aagaard


Radio frequency identification (RFID) is a key technology for the Internet of Things era. One important advantage of RFID over barcodes is that line-of-sight is not required between readers and tags. Therefore, it is widely used to perform automatic and unique identification of objects in various applications, such as product tracking, supply chain management, and animal identification. Due to the vulnerabilities of wireless communication between RFID readers and tags, security and privacy issues are significant challenges. The most popular passive RFID protocol is the Electronic Product Code (EPC) standard. EPC tags have many constraints on power consumption, memory, and computing capability. The field of lightweight cryptography was created to provide secure, compact, and flexible algorithms and protocols suitable for applications where the traditional cryptographic primitives, such as AES, are impractical. In these lightweight algorithms, tradeoffs are made between security, area/power consumption, and throughput.

In this thesis, we focus on the hardware implementations and optimizations of lightweight cryptography and present the Simeck block cipher family, the WG-8 stream cipher, the Warbler pseudorandom number generator (PRNG), and the WGLCE cryptographic engine.

Simeck is a new family of lightweight block ciphers. Simeck takes advantage of the good components and design ideas of the Simon and Speck block ciphers and it has three instances with different block and key sizes. We provide an extensive exploration of different hardware architectures in ASICs and show that Simeck is smaller than Simon in terms of area and power consumption.

For the WG-8 stream cipher, we explore four different approaches for the WG transformation module, where one takes advantage of constant arrays and the other three benefit from the tower field constructions of the finite field $\F_{2^8}$ and also efficient basis conversion matrices. The results in FPGA and ASICs show that the constant arrays based method is the best option. We also propose a hybrid design to improve the throughput with a little additional hardware.

For the Warbler PRNG, we present the first detailed and smallest hardware implementations and optimizations. The results in ASICs show that the area of Warbler with throughput of 1 bit per 5 clock cycles (1/5 bpc) is smaller than that of other PRNGs and is in fact smaller than that of most of the lightweight primitives. We also optimize and improve the throughput from 1/5 bpc to 1 bpc with a little additional area and power consumption.

Finally, we propose a cryptographic engine WGLCE for passive RFID systems. We merge the Warbler PRNG and WG-5 stream cipher together by reusing the finite state machine for both of them. Therefore, WGLCE can provide data confidentiality and generate pseudorandom numbers. After investigating the design rationales and hardware architectures, our results in ASICs show that WGLCE meets the constraints of passive RFID systems.