Guarding against the threat of clock attacks with analog IP

This Agile Analog blog post focuses on clock attacks and how clock attack monitors can help detect them. As system-on-chip (SoC) security threats grow even more sophisticated, attackers are increasingly targeting the clock system to manipulate execution timing and generate faults. By physically altering the clock signals, they can compromise cryptographic operations, bypass security mechanisms, or force a system change. Four primary techniques are used in physical clock attacks: clock glitching, frequency changing, single stepping, and duty cycle manipulation. The aim is to disrupt the normal operation of an electronics system by introducing malfunctions in order to exploit vulnerabilities or extract sensitive information.

The challenges with clock attacks

Software-based attacks are well documented, with established detection and countermeasures. However, hardware-level attacks, such as clock manipulation, remain more challenging to identify. There may be no immediately obvious indications of tampering so the impact might only become apparent after an extended period of time. Clock attacks specifically target low-level hardware components such as microcontrollers, cryptographic chips and processors. These often lack the same degree of monitoring and protection as higher-level software, making them more vulnerable to manipulation.

The impact of clock attacks

Clock attacks can have severe consequences, including system instability, security breaches, and also physical harm in security and safety-critical applications.

Data loss and corruption: Even minor disruptions to the clock signal can lead to data loss and corruption. Many embedded systems rely on precise timing, and a successful attack can force errors that compromise sensitive data.

System failure: Modern processors often require tightly controlled timings to ensure the correct process flow and execution of instructions. By glitching the clock, an attacker can introduce errors into processes that result in system failure or damage.

Safety risks: IoT devices have real-time constraints, where timing deviations can disrupt critical functions. A clock attack on a smart medical device, for example, could alter dosage calculations or deactivate life-saving monitoring systems.

Cryptographic vulnerabilities: encryption and key management depend on accurate timing for secure operations. If an attacker manipulates the clock, this can weaken cryptographic defenses and potentially allow encryption keys to be stolen.

Hardware compromise: Devices with secure boot mechanisms count on controlled timing to validate and load trusted firmware. By performing clock glitches at the right moment, an attacker could bypass security checks and upload malicious firmware.

Clock attacks are an active and growing concern. Without proper countermeasures, these vulnerabilities can be exploited to compromise critical systems, from payment cards to automotive control units. Given these risks, organizations must implement ways to detect and respond to clock-based tampering. This is where clock attack monitors play a crucial role in guarding embedded and cryptographic systems.

The benefits of using clock attack monitors

Clock attack monitors are security mechanisms designed to detect and mitigate clock attacks or other timing-related attacks on systems. These monitors typically track and analyze the timing behavior of hardware to identify unusual activity that could indicate tampering, for example, unexpected frequency changes or unsynchronized clock states.

Benefits of clock attack monitors include:

Continuous monitoring and immediate action: Clock attack monitors can provide continuous, real-time surveillance of a system's clock and timing behavior. By recognizing warning signs of a clock attack early the monitor can quickly trigger countermeasures, raising the alarm or isolating impacted areas if necessary, preventing or limiting damage by attackers trying to exploit a system.

Increased system integrity and reliability: Clock attack monitors can detect any tampering or irregularities in the clock signals, which helps to maintain the integrity and reliability of the system. The stringent ongoing checks ensure that the system’s behavior remains within expected boundaries.

Protection of cryptographic systems: Cryptographic algorithms could be vulnerable to timing attacks that manipulate variations in clock cycles to extract sensitive data such as secret keys. Clock attack monitors can detect attempts to exploit a system’s clock; for example, if there is a timing error during key generation, this could indicate that an attack is in progress.

Protection of embedded and IoT devices: Embedded systems and IoT devices may not include advanced security features, making them susceptible to clock-based attacks. A clock attack monitor provides an additional layer of protection. For example, a monitor could detect if an IoT device’s clock is being tampered with to influence sensor readings, preventing attackers from exploiting this.

Protection against secure boot and firmware tampering: Many systems use secure boot processes to verify that there is only trusted firmware. Clock glitching can interfere with the boot process, sidestepping security checks or allowing an attacker to load malicious firmware. A clock attack monitor can detect unusual timing deviations during boot and prevent unauthorized firmware from being loaded.

Reduced false positives: Modern clock attack monitors are highly efficient, providing comprehensive security. Unlike some security mechanisms that may trigger false positives or impact system performance, clock attack monitors are designed to detect genuine threats without causing unnecessary disruptions to normal operations.

Recent advances in clock attack monitors

Clock attack monitors provide robust tamper detection, guarding against hardware-level attacks that manipulate the timing of a system to exploit vulnerabilities. Recently, there have been new product advances in this space. Agile Analog offers novel customizable multi-process analog IP, including anti-tamper solutions. Our agileCAM product is a mixed-signal ring oscillator (RO)-based clock attack monitor designed to detect clock attacks involving changes in clock frequency, clock hold, and clock glitches errors. It provides frequency measurement with programmable alarm thresholds. The RO-based scheme is easily configurable depending on the frequency of the input clock and provides an area- and power-efficient solution.

To read more about Agile Analog’s clock attack monitor, please go to our agileCAM web page.

For a wider view of our tamper detection range, please visit our Security IP section.