Cost and Scalability of Hardware Encryption Techniques

Abstract

We discuss practical details and basic scalability for two recent ideas for hardware encryption for trojan prevention. The broad idea is to encrypt the data used as inputs to hardware circuits to make it more difficult for malicious attackers to exploit hardware trojans. The two methods we discuss are data obfuscation and fully homomorphic encryption (FHE). Data obfuscation [5] is a technique wherein specific data inputs are encrypted so that they can be operated on within a hardware module without exposing the data itself to the hardware. FHE is a technique recently discovered to be theoretically possible [2]. With FHE, not only the data but also the operations and the entire circuit are encrypted. FHE primarily exists as a theoretical construct currently. It has been shown that it can theoretically be applied to any program or circuit [2]. It has also been applied in a limited respect to some software [4]. Some initial algorithms for hardware applications have been proposed [1]. We find that data obfuscation is efficient enough to be immediately practical, while FHE is not yet in the practical realm. There are also scalability concerns regarding current algorithms for FHE.