2026-cawthon-fountain-codes-censorship
findings extracted from this paper
Encrypted DNS has attractive anti-blocking properties for circumvention rendezvous, but its constraint of conveying only small amounts of data per message makes it difficult to use as a generic data-exchange channel. Fountain codes offer an uncomplicated way to transmit discrete, bounded-length messages over such channels, including those that are unordered or unreliable.
Fountain codes (rateless erasure codes) break a message into many small, specially encoded pieces that can be reconstructed from any sufficient subset, making them well-suited to covert channels that are lossy, unordered, or bandwidth-constrained — properties common to DNS-based rendezvous channels.
Drawing on the Collage and Assemblage censorship-circumvention systems — which use fountain codes in conjunction with steganography — this work narrows focus to the rendezvous step alone, treating fountain codes as a standalone design component useful independently of steganographic cover channels.
A proof-of-concept implementation over UDP demonstrates the essential elements of fountain-code–based rendezvous: breaking a message into pieces, transmitting them over a lossy channel, and reconstructing them at the receiver. The authors also work out a prospective design for rendezvous over encrypted DNS.