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I am learning about Tor and Onion routing and I'm trying to compare both services. From the wiki link, I can see that Diffie Hellman (DH) handshake is used and when look into the “tor-design.pdf” for Tor, I see that DH is still used.
Since onion routing has been patented, I can't find any source which leads me to the design of onion routing. Can someone clarify this point about signatures in both services? Links to support it would be welcome.
As far as I can see it from the original onion routing patent, OR uses long term public keys for encrypting messages for onion routers and there is no description of a key exchange.
Tor can be seen as the second generation onion routing (and is intended to have no patent) and besides adding much more features (adding perfect forward secrecy, congestion control, directory servers, integrity checking, configurable exit policies) it uses a technique denoted as telescoping circuits, which on the one hand brings other features (such as forward secrecy) but also helps to circumvent patent issues with the original OR patent (as it does no longer apply the original "long term key" method proposed in the patent).
Basically, the idea of telescoping circuits is that a sender negotiates a short-term session key with each node along a path, and uses this key to encrypt the onion layers. Thereby, Diffie-Hellman is is used for key exchange with the onion routers and the negotiated session keys are AES keys.
