Flow

Manufacturing

Prepare programmer

• Generate a private key inside the programmer
• Provision certificate to the programmer
• Program signed firmware to the programmer
• Key exchange between a programmer and cloud server
  • Compute a shared key

Export package

• Upload firmware for target boards to cloud server
• Cloud server encrypts package information with shared key
  • The resulting cipher text (package) can be downloaded to OEM’s PC. It can then be sent to CM.

Import package

• Import the cipher text (package) to the programmer
• The package information is stored in the flash of the programmer
  • Production limit (over-production protection)
  • Token (for downloading signed firmware)

Device authentication provisioning

• Register a target board on the cloud server
• Generate a private key inside the target board
• Provision certificate to the target board

Firmware provisioning

• Ask server to create keypairs for secure boot on target board
• Program public keys for secure boot to target board
• Signed firmware is transmitted to programmer over HTTPS.
• Program bootloader firmware(BL2) to target board via SWD
• Securely program app firmware(BL3) to target board via ISP UART

Maintenance

Firmware upgrade

• The server checks if the version number of firmware is greater than that of the target board.
• Signed firmware is transmitted to programmer over HTTPS.
• Securely program app firmware(BL3) to target board via ISP UART