Target hardware is a rather low-powered MCU (ARM Cortex-M3 @72MHz, with just about 64KB SRAM and 256KB flash), so walking the thin line here. My board does have ethernet, and I will eventually get lwIP (lightweight TCP/IP FOSS suite) running on it (currently struggling). However, I also need some kind of super light-weight alternative to SSL/TLS. I am aware of the multiple GPL’d SSL/TLS implementations for such MCU’s, but their footprint is still fairly significant. While they do fit-in, given everything else, don’t leave much room for others.
My traffic is not HTTP, so I don’t have to worry about HTTPS, and my client/server communication can be completely proprietary, so non-standard solution is okay. Looking for suggestions on what might be the minimalistic yet robust (well a weak security is worthless), alternative that helps me —
- Encrypt my communication (C->S & S->C)
- Do 2-way authentication (C->S & S->C)
- Avoid man-in-middle attacks
I won’t be able to optimize library at ARMv7 assembly level, and thus bank entirely on my programming skills and the GNU-ARM compiler’s optimization. Given above, any pointers of what might be the best options ?
If any of those small TLS implementations allow you to disable all X.509 and ASN.1 functionality and just use TLS with preshared-keys you’d have quite a small footprint. That’s because only symmetric ciphers and hashes are used.