Q: How to implement secure OTA firmware updates on embedded Linux devices?
Answer
Secure OTA on embedded Linux: (1) Use A/B partition scheme – write to inactive partition verify then switch boot. (2) Authenticate with asymmetric signature: sign firmware with Ed25519/RSA-2048 private key verify on-device with public key stored in OTP or eFuse. (3) Use Mender SWUpdate or RAUC as the update framework – all support A/B and signed updates. (4) Always use HTTPS (TLS 1.3) for download. (5) Store the download in a tmpfs to avoid wearing flash. (6) Include rollback protection: set a non-volatile update counter in u-boot env or eMMC RPMB partition. (7) Verify checksums (SHA-256) before flashing. (8) Log all update attempts with timestamps. (9) Have a recovery mechanism: if update fails after N retries boot from the known-good partition.
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