Integrate TPM 2.0 with DICE on STM32 for Secure Boot and Firmware Integrity

Integrating a TPM 2.0 Root of Trust with DICE Architecture on STM32 Microcontrollers for Secure Boot and Firmware Integrity Verification

This tutorial walks you through the integration of a Trusted Platform Module (TPM) 2.0 with the DICE (Device Identifier Composition Engine) architecture on STM32 microcontrollers to establish a secure boot process and ensure firmware integrity verification. By leveraging the TPM, we can create a robust root of trust for your embedded applications.

Prerequisites

• Basic knowledge of embedded systems and microcontrollers.
• Familiarity with TPM 2.0 concepts.
• STM32 development board (e.g., STM32F4, STM32L4).
• TPM 2.0 module compatible with your STM32 board.
• Development environment set up (e.g., STM32CubeIDE).
• Firmware development knowledge in C/C++.

Parts/Tools

• STM32 development board
• TPM 2.0 module
• Connecting cables (e.g., jumper wires)
• STM32CubeIDE
• TPM 2.0 software stack (e.g., TSS or tpm2-tools)
• Serial terminal for debugging

Steps

1. Setup the Hardware
   1. Connect the TPM 2.0 module to the STM32 board using I2C or SPI interface.
   2. Ensure power supply to both the STM32 and the TPM module.
   3. Verify connections using a multimeter.
2. Install Required Software
   1. Download and install STM32CubeIDE.
   2. Install the TPM 2.0 software stack from the official repository.
   3. Set up the development environment by creating a new STM32 project.
3. Configure the TPM
   1. Initialize the TPM by calling the appropriate TPM initialization functions.
   2. Load the TPM 2.0 driver in your STM32 project.

   
   #include "tss2_sys.h"
   
   // Initialize TPM
   TSS2_SYS_CONTEXT *sapi_context;
   TSS2_RC rc = Tss2_Sys_Initialize(&sapi_context, ...);
   

4. Implement DICE Architecture
   1. Define the DICE components in your firmware.
   2. Implement the DICE structure for device identity and attestation.

   
   typedef struct {
       uint8_t device_id[16];
       uint8_t firmware_hash[32];
   } dice_t;
   

5. Secure Boot Process
   1. Implement a secure bootloader that verifies firmware integrity using the TPM.
   2. Use the TPM to measure and extend the firmware hash into the PCR (Platform Configuration Register).

   
   TSS2_RC rc = Tss2_Sys_PcrExtend(...); // Extend PCR with firmware hash
   

6. Firmware Integrity Verification
   1. Use the TPM to sign the firmware hash.
   2. Verify the signature during boot to ensure the integrity of the firmware.

   
   rc = Tss2_Sys_Sign(...); // Sign the measured firmware hash
   

7. Testing and Validation
   1. Test the secure boot process by flashing the firmware to the STM32 board.
   2. Use a serial terminal to observe boot messages and verify integrity checks.

Troubleshooting

• TPM Not Responding: Check power connections and I2C/SPI settings in the firmware.
• Firmware Fails to Boot: Ensure the firmware hash is correctly measured and extended into the TPM.
• Signature Verification Fails: Double-check the signing process and ensure the public key is correctly loaded.

Conclusion

Integrating a TPM 2.0 root of trust with the DICE architecture on STM32 microcontrollers provides enhanced security for embedded systems. By following this tutorial, you should now have a secure boot process in place, which ensures firmware integrity and device identity. Continue to explore advanced features of the TPM and DICE to further secure your applications.