How to Identify Hardware Trojans: Methods for Detection

If you work in the field of cyber security, you often hear about the term 'Hardware Trojan', often abbreviated as 'HT'.

Hardware Trojan is any modification in the circuitry of the Integrated Circuits(ICs) with malicious intentions. Modification in the IC circuit that leads to hardware trojan may be introduced at the time of the design or fabrication phase.

As we know the manufacturing process of ICs is fabless. The term "fabless" means the designing of hardware in one place or country and the actual manufacturing of silicon wafers or chips in another place or country. So it is challenging to identify the real source of contamination

Please understand that most of the techniques available to identify HTs are based on specific behaviors and attributes. Furthermore, if you employ an arbitrary method to detect trojans, the chances of failure are considerably higher. This blog provides you with a brief overview of methods of detection of hardware trojan or HT in the ICs.

Attributes of Hardware Trojans

• Hardware Trojan is usually small in size
• Generally passive as it triggers only after getting some specific input

Challenges in identification of Hardware Trojans

• The size of HT is too small
• Reverse engineering is very difficult, costly, and time-consuming
• There is no guarantee that no HT will be available in the remaining circuit
• HT is specifically constructed for stealth purposes.

Identify Hardware Trojans - Methods for Detection

Before starting the methods to identify hardware trojans, remember one thing "No method can identify the trojan with 100 percent accuracy". This simply means no method can guarantee for identification of all Trojans in the IC. However, there are still some methods to identify Trojans.

Prevention Techniques to Identify Trojans During Design and Fabrication

Identify Risks of Hardware Trojans introduced in the early phase of production

Review of Design

Employ techniques for supply chain security during production

Employ innovative technologies to mitigate the risks of counterfeit products

Techniques to Identify Trojans After Fabrication

Destructive	Non-Destructive
Method - Optical Expensive and time-consuming	Methods - Run Time and Test Time Include side-channel analysis

Destructive method - It involves reverse engineering technique to unfold different layers of ICs with the powerful microscope including the optical microscope and then compare the design and placement of different gates with the original design. Golden design is required to identify the trojan in this method.

Non-Destructive Methods

Run Time - Analyze the behavior of the device while running and compare it with the ideal results to identify the discrepancy. It is recommended to use error detection methods to detect trojans in FPGA and system-on-chip (SoC)

Test Time - This method is based on the logic testing approach. Different test cases are used as input to identify any unusual behavior of output.

Side Channel Analysis - One of the best methods to detect hardware trojans by analysis of leakage of physical parameters during run time of ICs. Physical parameters such as acoustic, EMI/EMC, power, etc. are used to determine secret cryptographic keys.