Tag: modems

All the articles with the tag "modems".

• Encrypted Chat Over Sound: An Acoustic MFSK Modem in Rust

  30 Aug, 2026

  I wrote a program that sends encrypted chat between two laptops using nothing but a speaker and a microphone. No network, no pairing, no passphrase — the peers agree a key over the air with X25519 and you verify it by reading four words aloud. Here is the whole stack: parallel MFSK modulation, Goertzel detection, Reed–Solomon with cross-block interleaving, half-duplex carrier sense, and AES-256-GCM with a short authentication string.