Side-Channel Attack Avoidance and Mitigation Through Asynchronous Digital Design
John M. Emmert, Anvesh Perumalla · 2025
An exploitable weak point in synchronous, clocked digital integrated circuits (ICs) and systems that are fabricated at untrusted facilities is the side channel attack (SCA). By inserting and leveraging Trojan circuits and monitoring side channels, a malicious, untrusted agent or entity can steal sensitive or personal information like credit card pins or cryptographic keys. Side channel attacks make use of indirect measures to exploit either existing or added Trojan circuitry to obtain secret or private information. Asynchronous or clockless digital design can be leveraged to combat and mitigate SCAs. There are different types of asynchronous design techniques ranging from locally clocked to clockless, and each has its own advantages and disadvantages. One type of clockless logic circuit is based on Null Convention Logic (NCL). In this chapter we describe simple techniques to design basic, asynchronous NCL circuits. Then, we go on to describe limitations and some methodologies that have been developed to overcome them.