ECHO · THE RELAY
Infrastructure, assumed hostile.
Reference relay v0.1 · stores sealed boxes · cannot open them
The relay is the one piece of Echo that lives on a server you don't control. So it is built to hold nothing but ciphertext — and to keep working even if the server itself is the adversary.
A correct design holds when the server is the adversary. This page runs that design, for real, in your browser.
Two devices, one encrypted memory, a relay that never sees it.
Device A encrypts a memory on-device, pads it, and uploads. The relay stores the opaque bytes. Device B — sharing the vault key out-of-band, never through the relay — syncs, downloads, and decrypts locally. The vault key and the plaintext never leave the browser.
Real Ed25519 + AES-256-GCM run in your browser. Open DevTools → Network and watch: only ciphertext ever leaves this page.
The relay is built to be untrusted.
Every write is signed with the device's Ed25519 key over METHOD·PATH·TS·NONCE·SHA256(body). No valid signature, no access.
Sealed boxes are padded to fixed sizes, so the relay learns nothing from the length of what you store.
A best-effort safety net that rejects anything that looks like plaintext or a recovery fragment. It catches a buggy client — it is never a guarantee.
Each nonce is single-use (shared store), bodies are size-capped before they're read, and each vault has device and storage quotas. The server assumes it is under attack.
The honest edge (Law 6): the relay sees no content, ever — but it does observe metadata like timing, sizes (bucketed), and which device is talking. Echo keeps "no content" absolutely; it never claims "no metadata."