Functional encryption of integrated circuits by key-based hybrid obfuscation

This paper proposes a novel technique to functional encryption of integrated circuits (ICs) termed as hybrid obfuscation. Functional encryption or hardware obfuscation refers to a set of countermeasures used to protect circuits against attacks and illegal use during manufacturing at untrusted global foundries. The goal of encryption is achieved at the design house by functional modifications to the design and embedding secret keys. These keys are only programmed onto the chip once they are received from the foundry. Because the untrusted foundry does not have access to the key, it cannot sell excess parts as the chip won't function correctly without the key. By combining existing techniques of obfuscation known as fixed obfuscation and dynamic obfuscation, the hybrid obfuscation technique achieves the goals of functional encryption. An analysis of security measures shows that the hybrid obfuscation improves the security of a design by times compared to fixed obfuscation, where K is the key size in bits. Also, the hybrid obfuscation reduces area overhead by 40% and power overhead by 30% for a key size of 30 bits compared to the dynamic obfuscation. Thus, the hybrid obfuscation technique offers a solution which is between that of fixed and dynamic obfuscation.