Quick Overview: Understanding Hardware Trojans

Hardware Trojan (HT) is a tiny piece of hardware circuitry available on IT hardware with malicious intentions. You can take an example of access to hardware without proper authentication and authorization methods.

Physical and logical parameters, including particular temperatures and humidity, wireless signals, etc. may activate hardware Trojans.

Types of Circuitry in Hardware Trojan

Hardware Trojan circuitry is divided into two types of circuitry:

• Trigger circuit - activate on achieving certain physical and logical parameters such as input signals, timing, or environmental factors to activate HT. Trigger circuitry is responsible for activating the malicious functionality of the hardware Trojan.
• Payload circuit - execution of the unintended function that is not mentioned in the specification after activation of HT. Payload circuitry can be designed to leak sensitive data, disable the device, or create vulnerabilities.

Purpose of Hardware Trojan

The primary purpose of using a hardware trojan in an IC circuit is to bypass the security functionality to access the IT hardware or for information leakage. HT can disable or destroy the whole chipset available on the hardware.

HT encompasses espionage by stealing data, sabotaging normal operations, data manipulation, creating backdoors for unauthorized access, counterfeiting, and DoS attacks.

HTs can compromise sensitive systems, intellectual property, and supply chains, posing grave security threats. Detection and prevention are crucial for preserving system trust and security.

Types of Hardware Trojans

Types of Hardware Trojan	Description	Use Case	Identification Tools
Gate-Level Trojans	Alter the functionality of individual gates within a chip, potentially disrupting logical operations.	Manipulating encryption algorithms leads to compromised data security.	Gate-level simulation tools, Formal Verification tools, Scan Chain Testing.
Netlist-Level Trojans	Introduce malicious components into the netlist, impacting the connections between various modules.	Sabotaging communication protocols in a networked system.	Netlist analysis tools and formal Verification tools.
Layout-Level Trojans	Modify the physical layout of the chip, such as the placement of transistors, to create vulnerabilities.	Tampering with critical components in a processor causes performance issues.	Layout-aware testing tools and side-channel analysis tools.
Hardware Trojans via Dopant	Introduce intentional doping in semiconductor materials to alter the electrical behavior of components.	Modifying power characteristics to affect power consumption profiles.	Scanning Electron Microscopy, Optical Fault Injection tools.
Trojans via Additional Circuit	Insert extra circuitry that activates under specific conditions, compromising the chip's integrity.	Scanning Electron Microscopy and optical Fault Injection tools.	Logic Analyzer, Side-channel analysis tools.
Backdoor Trojans	Create covert access points that allow unauthorized parties to control or manipulate the hardware remotely.	Providing remote access to a chip for unauthorized control or data exfiltration.	Security-focused code analysis tools, Intrusion Detection Systems.
Analog Trojans	Manipulate analog components like resistors or capacitors, affecting the performance of analog circuits.	Distorting analog sensor readings in critical applications, like medical devices.	Analog signal analysis tools, Hardware Trojans Detection Frameworks.
Supply Chain Trojans	Compromise the manufacturing or distribution process, leading to the insertion of trojans during production.	Modifying components during fabrication to compromise a device's security.	Supply chain audits, Trusted Foundry Programs.
Power Side-Channel Trojans	Exploit variations in power consumption to leak sensitive information or disrupt the normal functioning.	Exploit variations in power consumption to leak sensitive information or disrupt normal functioning.	Power analysis tools, Differential Power Analysis countermeasures.
Fault-Injection Trojans	Introduce faults or errors under specific conditions, potentially causing the chip to behave unpredictably.	Triggering faults in safety-critical systems to cause malfunctions.	Fault injection tools, Fault tolerance testing.
Configuration Bit Trojans	Manipulate configuration bits or memory elements to change the behavior of the device upon activation.	Changing device settings to create vulnerabilities or alter functionality.	Configuration auditing tools, and Bitstream analysis tools.
Memory Trojans	Alter the content of memory cells, leading to unauthorized access or modification of stored information.	Modifying critical data in memory to impact system behavior or security.	Memory integrity checking tools, Memory forensics tools.
I/O Trojan	Affect the input or output functionalities of the chip, potentially leading to data leakage or manipulation.	Affects the input or output functionalities of the chip, potentially leading to data leakage or manipulation.	I/O monitoring tools, Boundary Scan Testing.

Detection of Hardware Trojan

Test Methods used for the detection of Hardware Trojans are under research. It is tough to identify HT by using traditional methods. Below are some ways available to locate HT on the IT hardware. Countermeasures include physical inspection, side-channel analysis, functional testing, and secure supply chain practices. Mitigating hardware Trojan risks is vital to safeguarding critical infrastructure, military systems, intellectual property, and data privacy. You may refer additional blog on the Method of Detection of Hardware Trojans.

Side Channel Analysis - Detecting hardware Trojans using side-channel analysis involves collecting unintended information leakage like power consumption, and then analyzing this data for anomalies. All IT hardware emits different signals that include electrical, magnetic, acoustic, etc. Statistical techniques and machine learning are often employed for pattern recognition. It's a specialized and ongoing challenge in hardware security, requiring expertise and access to target hardware. These residual signals may be utilized to identify malicious circuitry on the IC. Click Here to learn interview questions related to Side Channel Attacks.

Physical Checking of IC - This method involves the comparison of the circuit available on the chip with the actual chip with golden specifications. This method is not easy to detect hardware trojans. To identify hardware Trojans through physical inspection, examine a device's physical components, employ microscopes, X-rays, CT scans, FIB analysis, electron microscopy, and reverse engineering. Look for irregularities, hidden components, or modifications, and compare with trusted references. Expert analysis is crucial, though some Trojans may remain undetected if highly sophisticated.

Built-in Tests - Tester inserted a small piece of additional circuitry to identify IT hardware access or extract sensitive information.

Functional Testing - This involves the analysis of input and output obtained on the chip. HT could be identified if there is a deviation from the actual design. Test patterns, signal analysis, fault injection, and stress testing are employed to detect anomalies or deviations from expected behavior. It complements other methods like physical inspection and is essential for robust hardware security assessment.

Conclusion

This blog provides you with a brief overview of Hardware Trojan. This blog explains Hardware Trojans and their malicious purposes, including data theft and system sabotage, and highlights the methods of detecting and preventing these Trojans.