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o Major features:
- Tor now supports a new circuit extension handshake designed by Ian
Goldberg, Douglas Stebila, and Berkant Ustaoglu. Our original
circuit extension handshake, later called "TAP", was a bit slow
(especially on the server side), had a fragile security proof, and
used weaker keys than we'd now prefer. The new circuit handshake
uses Dan Bernstein's "curve25519" elliptic-curve Diffie-Hellman
function, making it significantly more secure than the older
handshake, and significantly faster. Tor can either use one of two
built-in pure-C curve25519-donna implementations by Adam Langley,
or link against the "nacl" library for a tuned version if present.
The built-in version is very fast for 64-bit systems building with
GCC. (About 10-14x faster on the server side, and about 7x faster
on the client side.) The built-in 32-bit version is still faster
than the old TAP protocol (about 3x), but using libnacl would be
better on most 32-bit x86 hosts.
Clients don't currently use this protocol by default, since
comparatively few clients support it so far. To try it, set
UseNTorHandshake to 1.
Implements proposal 216; closes ticket #7202.
- Tor servers and clients now support a better CREATE/EXTEND cell
format, allowing the sender to specify multiple address, identity,
and handshake types. Implements Robert Ransom's proposal 200;
closes ticket #7199.
o Code simplification and refactoring:
- Split the onion.c file into separate modules for the onion queue
and the different handshakes it supports.
- Remove the marshalling/unmarshalling code for sending requests to
cpuworkers over a socket, and instead just send structs. The
recipient will always be the same Tor binary as the sender, so
any encoding is overkill.
o Testing:
- Add benchmark functions to test onion handshake performance.
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