A secure computer is essentially in a faraday box, and to deal with cooling, would be full of mineral oil. I have read about Van Eck phreaking lately, and I don't think I see much in academia about it. Sure, there's some successful attempts to derive RSA keys from laptops, but apparently keyboards are vulnerable ( https://lasec.epfl.ch/keyboard/ )? LCD monitors leak their contents(not a big deal just shelve this away and forget about it)? The Inslaw Affair involved a backdoor in Promis using side channel emissions? Has anyone attempted to see how much signal leaks from telephone lines? Or from ethernet cables? Would an algebraic relationship between ciphertext bits make it easier for discover the key? Is an MDS matrix necessary for linear diffusion? Everything is so cheap nowadays, a software defined radio can be had for $20. https://github.com/martinmarinov/TempestSDR More impressive than a cryptographic attack against key fobs would be a way to eavesdrop on all the communications on a telephone line. That'd cause the immediate adoption of the Clipper Chip! The academic community for cryptography is strange, no null results are published anywhere. It'd be useful to have a casual wiki for those. Even if a novel cryptographic technique that requires more plaintext than bruteforce for ChaCha is discovered, it would have the potential to be improved upon.