nRF54L Series Express

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Tamper detection

The nRF54L Series devices are equipped with various detectors to recognize and react upon physical tampering attempts. Physical security and protection against physical manipulation is a new feature on the nRF54L Series devices that is important for establishing comprehensive security against both digital and physical threats. However, it is worth noting that tamper detection is not an exact science and it is difficult to detect every kind of physical attack with complete certainty.

The Tamper Controller implements the following physical security features:

  • Active driven shield mounted on PCB on top of device to detect external tampering attacks
  • Detection of fault injection attacks
    • Glitch detector (GLITCHDET) to monitor supply voltages. When this detector is triggered, it automatically issues a reset.
    • Signal protector to guard critical configuration signals
    • Glitch detectors (TAMPC) to detect timing violations of internal logic
    • Separate internal correctness self-check for CRACEN

This section will cover the detectors listed above and how the nRF54L Series devices are protected against physical attacks. The tamper controller’s technical documentation can be found in the tamper controller documentation.

TAMPC controller

Active shield

The nRF54L Series devices have an active shield which detects physical access attempts against the device and its PCB level connections. The active shield works by generating a Pseudo-Random Bit Sequence (PRBS) on an output pin and detecting mismatches with the active shield between the input and output pins on each of its monitored channels. A mismatch means that a channel has been broken, and a physical tampering attack is ongoing.

If the active shield detects a physical tampering event in one of its channels, it will either raise a tampering event or trigger a system-wide reset with reason SECTAMPER depending on its configuration. For more information on the active shield, refer to the tamper controller documentation.

Signal protector

The nRF54L Series devices have detectors to protect selected signals that are controlling critical device features. The signal protector implements a detector per protected signal, identifying unintentional value changes caused by fault injection attacks. The detectors notify the tamper controller if a protected signal changes value caused by tampering. The detectors are enabled from reset and as they are passive, there is no active power consumption.

A detected unintentional value change in any of the protected signals leads to an internal tamper event. This will either raise a tampering event or trigger a system-wide reset with reset reason SECTAMPER depending on the configuration. Automatic reset is the default configuration.

Glitch detectors (TAMPC)

Glitch detectors provide security against fault-injection attacks such as voltage glitching and electromagnetic fault injection. A grid of detectors is strategically placed among the digital logic to detect local timing glitches, that is timing violations.

Fault injection detectors automatically activate after reset and can be disabled when not required or when the application does not request secure services. Tamper detection policy should be carefully planned and address relevant threats for your product.

When a fault injection attack such as voltage glitching occurs, technically the attack could bypass the detector and modify the logic signal before the detection occurs. However, it is good to note that the detectors are designed and tuned to be more sensitive to timing violations than normal logic, enabling the digital logic to react before an injected fault is propagated through the system.

The glitch detectors are enabled from reset. A detected internal tamper event will either raise a tampering event or trigger a system-wide reset with reset reason SECTAMPER depending on the configuration. Automatic reset is the default configuration. For more information, see the tamper controller documentation.

Physical security

The CRACEN security subsystem integrates countermeasures to protect against both differential power analysis (DPA) and fault injection attacks. The AES engine can apply random masking during the AES rounds to complicate the analysis of its power signature, while the Public Key Accelerator can detect faults injected during its internal key generation process.

Voltage glitch detector (GLITCHDET)

This detector is an analog detector with high bandwidth which detects rapid voltage glitches on supply pins, both positive and negative glitches. The current consumption for this detector is significant. The detector is enabled from device reset, and issues an automatic system reset if triggered.

It is recommended keep the detector enabled during secure boot, and then dynamically enable and disable the detector during runtime operation when security critical operations are executed based on the product’s threat model.

For more information, please see the technical documentation for voltage glitch detectors.

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