Logic locking has emerged as a promising solution to protect integrated circuits against piracy and tampering. However, the security provided by existing logic locking techniques is often thwarted by Boolean satisfiability (SAT)-based oracle-guided attacks. Criteria for successful SAT attacks on locked circuits include: (i) the circuit under attack is fully combinational, or (ii) the attacker has scan chain access. To address the threat posed by SAT-based attacks, we adopt the dynamically obfuscated scan chain (DOSC) architecture and illustrate its resiliency against the SAT attacks when inserted into the scan chain of an obfuscated design. We demonstrate, both mathematically and experimentally, that DOSC exponentially increases the resiliency against key extraction by SAT attack and its variants. Our results show that the mathematical estimation of attack complexity correlates to the experimental results with an accuracy of 95% or better. Along with the formal proof, we model DOSC architecture to its equivalent combinational circuit and perform SAT attack to evaluate its resiliency empirically. Our experiments demonstrate that SAT attack on DOSC-inserted benchmark circuits timeout at minimal test time overhead, and while DOSC requires less than 1% area and power overhead.
Does logic locking work with EDA Tools
Logic locking is a promising solution against emerging hardware security threats, which entails protecting a Boolean circuit using a “keying” mechanism. The latest and hitherto unbroken logic-locking techniques are based on the “corrupt-and-correct (CAC)” principle, offering provable security against input-output query attacks. However, it remains unclear whether these techniques are susceptible to structural attacks. This paper exploits the properties of integrated circuit (IC) design tools, also termed electronic design automation (EDA) tools, to undermine the security of the CAC techniques. Our proposed attack can break all the CAC techniques, including the unbroken CACrem technique that 40+ hackers taking part in a competition for more than three months could not break. Our attack can break circuits processed with any EDA tools, which is alarming because, until now, none of the EDA tools can render a secure locking solution: logic locking cannot make use of the existing EDA tools. We also provide a security property to ensure resilience against structural attacks. The commonly-used circuits can satisfy this property but only in a few cases where they cannot even defeat brute-force; thus, questions arise on the use of these circuits as benchmarks to evaluate logic locking and other security techniques.
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- USENIX Security Conference 2021
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- National Science Foundation
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