Every order. Rate, amounts, deadline, both addresses — signed at the moment your deposit address appears.
The canary. Every time.
Anything else claiming to come from us.
Served from the clearnet address and the onion address. Same key, both places.
Compare the fingerprint across both before you rely on it. If they differ, one of them is not us.
Good signature means the terms you saved are the terms we issued. A bad one means somebody edited them.
It proves the text came from this key. It does not prove the key is honest.
That is what the canary and time are for.