Hiding from Hardware Trojan Detectors by Avoiding Rare Events.

An important part of the defense against hardware trojans in commercially available chips is the research of detection techniques as well as the development of trojans challenging detection algorithms. The possible attack scenarios between register transfer level design and implemented silicon are manyfold and cannot be regarded at once. In this work a trojanic structure is presented that is inserted at design time and assumes a defender that is based on rare event detection as well as observability and controllability analysis (SCOAP). The introduced trojan escapes analysis based on these priciples, by avoiding rare events and abnormally large SCOAP values to blend with the original hardware. The proposed infection technique is generally able to alter the output of the attacked module to a malicious output, activated by an activation vector, independent of the module’s functionality. Applied to a simple Advance Encryption Standard (AES) module the area overhead introduced by the trojan is 0.15%.