Efficiency of Logic Minimization Techniques for Cryptographic Hardware Implementation

• Main Author: Raghuraman, Shashank
• Other Authors: Electrical and Computer Engineering
• Format: Others
• Published: Virginia Tech 2019
• Subjects: Logic synthesis; Cryptographic hardware; Circuit minimization; Leon-3; System-on-Chip; Authenticated encryption hardware
• Online Access: http://hdl.handle.net/10919/91462

With significant research effort being directed towards designing lightweight cryptographic primitives, logical metrics such as gate count are extensively used in estimating their hardware quality. Specialized logic minimization tools have been built to make use of gate count as the primary optimization cost function. The first part of this thesis aims to investigate the effectiveness of such logical metrics in predicting hardware efficiency of corresponding circuits. Mapping a logical representation onto hardware depends on the standard cell technology used, and is driven by trade-offs between area, performance, and power. This work evaluates aforementioned parameters for circuits optimized for gate count, and compares them with a set of benchmark designs. Extensive analysis is performed over a wide range of frequencies at multiple levels of abstraction and system integration, to understand the different regions in the solution space where such logic minimization techniques are effective. A prototype System-on-Chip (SoC) is designed to benchmark the performance of these circuits on actual hardware. This SoC is built with an aim to include multiple other cryptographic blocks for analysis of their hardware efficiency. The second part of this thesis analyzes the overhead involved in integrating selected authenticated encryption ciphers onto an SoC, and explores different design alternatives for the same. Overall, this thesis is intended to serve as a comprehensive guideline on hardware factors that can be overlooked, but must be considered during logical-to-physical mapping and during the integration of standalone cryptographic blocks onto a complete system. === Master of Science === The proliferation of embedded smart devices for the Internet-of-Things necessitates a constant search for smaller and power-efficient hardware. The need to ensure security of such devices has been driving extensive research on lightweight cryptography, which focuses on minimizing the logic footprint of cryptographic hardware primitives. Different designs are optimized, evaluated, and compared based on the number of gates required to express them at a logical level of abstraction. The expectation is that circuits requiring fewer gates to represent their logic will be smaller and more efficient on hardware. However, converting a logical representation into a hardware circuit, known as “synthesis”, is not trivial. The logic is mapped to a “library” of hardware cells, and one of many possible solutions for a function is selected - a process driven by trade-offs between area, speed, and power consumption on hardware. Our work studies the impact of synthesis on logical circuits with minimized gate count. We evaluate the hardware quality of such circuits by comparing them with that of benchmark designs over a range of speeds. We wish to answer questions such as “At what speeds do logical metrics rightly predict area- and power-efficiency?”, and “What impact does this have after integrating cryptographic primitives onto a complete system?”. As part of this effort, we build a System-on-Chip in order to observe the efficiency of these circuits on actual hardware. This chip also includes recently developed ciphers for authenticated encryption. The second part of this thesis explores different ways of integrating these ciphers onto a system, to understand their effect on the ciphers’ compactness and performance. Our overarching aim is to provide a suitable reference on how synthesis and system integration affect the hardware quality of cryptographic blocks, for future research in this area.