Canary
Warrant canary
This is a signed statement from the operator confirming they haven't been served with any secret government orders. It gets updated every quarter and is included in your login challenge so you see it each time you authenticate.
Current statement
This canary is not yet PGP-signed. The operator should generate a clearsigned version using their offline key.
What this actually does
In some countries, a government can force a service to hand over data AND gag them from telling anyone. But they typically can't force you to actively lie — they can compel silence, not false statements.
So the trick: keep publishing "we haven't been served" every quarter. If that statement disappears, or stops getting updated, or the PGP signature breaks — you know something happened, even though nobody said a word.