Signed chain and receipts

Everything that happens in a room is an entry in one append-only log. Entries are linked by hashes, so changing any entry breaks every link after it.

An entry

The sender signs an envelope: who sent it, on whose behalf, who may see it, and the payload. The host accepts it, gives it a sequence number and a time, links it to the previous entry, and writes it to the log. Nothing is edited or removed from the log afterwards, except that a room's end erases what the room says it erases.

Receipts

A receipt is the host's signed statement that the log reached a given length with a given head hash. Once you hold one, the host cannot quietly rewrite what came before it without being caught.

What you may see

You see the entries your scope allows. Each other entry reaches you as a stub: only its number and hashes. Your chain still links end to end, so you can check it without seeing other people's private messages.

Anything delivered with a field removed is a projection, signed by the host rather than the sender, so nobody is shown a changed message under the sender's name.

What it proves

The chain proves who signed what, in what order, and that it has not changed since. It does not prove a statement is true. It also cannot prove what happened outside the room.

The format is in the protocol. To check a chain yourself, see Browser verification.