S32K3 Questions Regarding HSE Physical Tamper Protection Function

[wuxianlong]

Hi ,NXP

I'm not quite clear about the working scenarios of HSE's physical tamper protection function. What kind of tampering methods is it designed to prevent?

I understand that Passive Tamper involves detecting the electrical level of an external device. If there is a change in the electrical level, it is considered as a tampering attempt. Could you provide an example?

I understand that Active Tamper involves short-circuiting HSE_TAMPER_EXTIN0 and HSE_TAMPER_LOOP_OUT0. If there is a discrepancy between the IN and OUT electrical levels, it is considered as a tampering attempt. Could you provide an example?

Best  Regards,
xianlong

[lukaszadrapa · Accepted solution]

Hi @wuxianlong 

Passive Tamper Detection
How it works:
Passive tamper detection monitors the electrical level (voltage) on a dedicated input pin (e.g., HSE_TAMPER_EXTINx). If the voltage level changes unexpectedly (e.g., from high to low or vice versa), it is interpreted as a tamper event.

Example Scenario:
Imagine a secure enclosure with a tamper switch connected to HSE_TAMPER_EXTIN0. When the enclosure is closed, the switch pulls the pin high (e.g., 3.3V). If someone opens the enclosure, the switch opens or pulls the pin low (e.g., 0V). This change in voltage is detected by the HSE as a tamper attempt.

Active Tamper Detection
How it works:
Active tamper detection involves a loop circuit where the HSE outputs a signal on HSE_TAMPER_LOOP_OUTx and expects to receive the same signal back on HSE_TAMPER_EXTINx. If the signal is altered or interrupted, it indicates a tamper attempt.

Example Scenario:
A secure loop wire runs through the device casing and connects HSE_TAMPER_LOOP_OUT0 to HSE_TAMPER_EXTIN0. The HSE sends a dynamic signal (e.g., a pseudo-random pattern) through the loop. If an attacker cuts the wire or tries to tap into it, the signal received at EXTIN0 will differ from what was sent, triggering a tamper alert.

These mechanisms are designed to detect events like:
Opening of device enclosures
Cutting or shorting of tamper detection lines
Probing or injecting signals into secure areas

Regards,

Lukas