SE Manager Tamper

This example uses the SE Manager API to demonstrate the tamper feature on the supported Series 2 Secure Vault device.

For demonstration purposes, a private command key is stored in the device’s memory to sign the access certificate for tamper disable. The device’s public command key in the SE OTP must match with the public key of this private command key to disable tamper signals.

The default private command key (cmd-unsafe-privkey.pem) can be found in the Windows folder below.

C:\SiliconLabs\SimplicityStudio\v5\developer\adapter_packs\secmgr\scripts\offline

The public key of cmd-unsafe-privkey.pem is:

X - B1BC6F6FA56640ED522B2EE0F5B3CF7E5D48F60BE8148F0DC08440F0A4E1DCA4

Y - 7C04119ED6A1BE31B7707E5F9D001A659A051003E95E1B936F05C37EA793AD63

If the device does not have public command key in the SE OTP, the program will prompt the user to program the public key above to the device.

The user can change the private command key (private_command_key[]) in app_se_manager_tamper_disable.c to match with the device’s public command key in the SE OTP for tamper disable.

The example redirects standard I/O to the virtual serial port (VCOM) of the kit. By default, the serial port setting is 115200 bps and 8-N-1 configuration.

The example has been instrumented with code to count the number of clock cycles spent in different operations. The results are printed on the VCOM serial port console. This feature can be disabled by defining SE_MANAGER_PRINT=0 (default is 1) in the IDE setting (Preprocessor->Defined symbols).

Tamper Responses

Level Responses Description
0 Ignore No action is taken
1 Interrupt The SETAMPERHOST interrupt on the host is triggered
2 Filter A counter in the tamper filter is increased
4 Reset The device is reset
7 Erase OTP Erases the OTP configuration of the device (make the device and all wrapped secrets unrecoverable)

Tamper Signals

Number Name Default level User level in this example
0 Reserved
1 Filter Counter 0 1
2 SE Watchdog 4 4
3 Reserved
4 SE RAM CRC 4 4
5 SE Hardfault 4 4
6 Reserved
7 Software Assertion 4 4
8 Reserved
9 UserCodeAuth 0 0
10 MailboxAuth 0 1
11 DCIAuth 0 0
12 OTP Read 4 4
13 Reserved
14 Self-test 4 4
15 TRNG Monitor 0 1
16 PRS0 0 1 (Push button PB0)
17 PRS1 0 1 (None)
18 PRS2 0 2 (Push button PB0)
19 PRS3 0 2 (None)
20 PRS4 0 4 (Push button PB1)
21 PRS5 0 4 (Software)
22 PRS6 0 7 (None)
23 PRS7 0 7 (None)
24 DECOUPLE BOD 4 4
25 TempSensor 0 2
26 VGlitch Falling 0 2
27 VGlitch Rising 0 2
28 SecureLock 4 4
29 SE Debug 0 0
30 Digital glitch 0 2
31 SE ICACHE 4 4

The disable tamper command simply reverts all masked tamper sources (TAMPER_DISABLE_MASK in app_se_manager_tamper_disable.h) to the hardcoded configuration (default levels in table above).

The default value of TAMPER_DISABLE_MASK is 0x00fa0000 so PRS7, PRS6, PRS5, PRS4, PRS3, and PRS1 are restored to the default level 0 (Ignore) after running the disable tamper command.

Tamper Settings

Setting User value in this example
Filter - trigger threshold 4
Filter - reset period ~33 seconds
Flags Digital Glitch Detector Always On: Disabled
Reset threshold 5

SE Manager API

The following SE Manager APIs are used in this example:

Getting Started

  1. Upgrade the kit’s firmware to the latest version (see Adapter Firmware under General Device Information in Simplicity Studio 5 Users Guide).
  2. Upgrade the device’s SE firmware to the latest version (see Secure Firmware under General Device Information in Simplicity Studio 5 Users Guide).
  3. Open any terminal program and connect to the kit’s VCOM port (if using Device Console in Simplicity Studio 5, Line terminator: must be set to None).
  4. Create this platform example project in the Simplicity IDE (see Examples in Simplicity Studio 5 Users Guide, check Platform() checkbox to browse the platform examples).
  5. Build the example and download it to the kit (see Simple Build and Flash Programmer in Simplicity Studio 5 Users Guide).
  6. Run the example and follow the instructions shown on the console.

Additional Information

  1. The hard-coded private command key is an insecure method so the user should find a way to import the signed access certificate for tamper disable.
  2. The device should disconnect from the debugger when running this example.
  3. Warning: Loading the tamper configuration and a public command key into the SE are a ONE-TIME-ONLY process. Both of these assignment operations are irrevocable and persist for the life of the device.
  4. The default optimization level is Optimize for debugging (-Og) on Simplicity IDE and None on IAR Embedded Workbench.

Resources

AN1247: Anti-Tamper Protection Configuration and Use