Write walking onions specification

Walking onions is a set of protocols improving scalability for the Tor network by enabling constant-size scaling of the information each client must download. Walking Onions will allow us to remove nearly all directory overhead from the Tor protocol, enabling Tor to scale to many more clients and relays, with no reduction in security.

The proposal is at https://gitweb.torproject.org/torspec.git/tree/proposals/300-walking-onions.txt

This ticket is a complete, byte-level specification of the Walking Onions design, in sufficient detail to permit independent implementations of Walking Onions to interoperate. This will include a description of all new directory formats, all new wire protocols, all new client and relay behaviors, and all backward compatibility mechanisms.

Activities:

• Write an initial draft of specification, identifying unknowns and options in the design.
• Distribute draft to tor-dev mailing list and to researchers for comment.
• Take decisions on all unknowns and options; if uncertainty remains.
• Write or locate reference-implementations for any primitive operations not already used by Tor.Write reference implementations for all novel encodings/decodings.