Q: How to implement end-to-end TLS security for IoT devices with certificate authentication?
Answer
For embedded TLS on IoT devices: (1) Use TLS 1.2 minimum – TLS 1.3 is preferred for lower latency. (2) Use mbedTLS or wolfSSL for embedded TLS stacks (50-250 KB RAM). (3) Use ECC P-256 certificates instead of RSA-2048 for smaller key size and faster handshake. (4) Store certificates in provisioned flash/OTP – never in firmware. (5) Implement certificate chain validation (intermediate CAs). (6) Use mutual TLS (client certificate) for device-to-cloud authentication. (7) Use a TLS session resumption mechanism to avoid full handshake on reconnect. (8) Implement secure key storage using STM32 HSM or ARM TrustZone. (9) Use certificate pinning to prevent MITM from rogue CAs. For microcontrollers with <64 KB RAM use pre-shared key (PSK) mode or Raw Public Key (RPK) mode to reduce overhead.
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