F26-TO: Yes
Rationale
Tor requires an existing circuit associated with the receiving connection before forwarding RELAY or RELAY_EARLY cells. A missing circuit causes a drop at the transit relay; circuit creation and extension establish the local forwarding state. This gates onward overlay transmission on connection-scoped circuit admission, rather than only checking the final onion service.
Assessment method
Primary normative source and selected adjacency-policy analysis; no execution
Source context
Tor Specifications: circuit-ID checks, circuit creation and forwarded-cell digest scope
Outstanding qualification
Credit only the circuit-state boundary on the selected TLS relay connections. Circuit IDs are not secret credentials, and clients may create valid circuits without a final-service allowlist. An admitted peer or circuit owner can still send abusive traffic; creation costs and incoming IP bandwidth are already spent. Forwarded cells are not digest-authenticated at every intermediate hop: unrecognized cells continue along an existing circuit. No full DDoS immunity, bandwidth reservation or runtime test is claimed.
Public sources
- https://spec.torproject.org/tor-spec/routing-relay-cells.html
- https://spec.torproject.org/tor-spec/creating-circuits.html
- https://spec.torproject.org/tor-spec/create-created-cells.html
- https://spec.torproject.org/tor-spec/relay-cells.html
Editorial evidence references
The following identifiers refer to research records not included in this public package; they are not public links.
- round455.html
- round455-sources.json