When a router posts a signed descriptor to a directory authority, the authority first checks whether it is well-formed and correctly self-signed. If it is, the authority next verifies that the nickname in question is not already assigned to a router with a different public key. Finally, the authority MAY check that the router is not blacklisted because of its key, IP, or another reason.
An authority also keeps a record of all the Ed25519/RSA1024 identity key pairs that it has seen before. It rejects any descriptor that has a known Ed/RSA identity key that it has already seen accompanied by a different RSA/Ed identity key in an older descriptor.
At a future date, authorities will begin rejecting all descriptors whose RSA key was previously accompanied by an Ed25519 key, if the descriptor does not list an Ed25519 key.
At a future date, authorities will begin rejecting all descriptors that do not list an Ed25519 key.
If the descriptor passes these tests, and the authority does not already have a descriptor for a router with this public key, it accepts the descriptor and remembers it.
If the authority does have a descriptor with the same public key, the newly uploaded descriptor is remembered if its publication time is more recent than the most recent old descriptor for that router, and either:
- There are non-cosmetic differences between the old descriptor and the new one. - Enough time has passed between the descriptors' publication times. (Currently, 2 hours.)
Differences between server descriptors are "non-cosmetic" if they would be sufficient to force an upload as described in section 2.1 above.
Note that the "cosmetic difference" test only applies to uploaded descriptors, not to descriptors that the authority downloads from other authorities.
When a router posts a signed extra-info document to a directory authority, the authority again checks it for well-formedness and correct signature, and checks that its matches the extra-info-digest in some router descriptor that it believes is currently useful. If so, it accepts it and stores it and serves it as requested. If not, it drops it.