Just wondering, which protocol, TAP or NTor is less computationally intensive for a relay to process and why ?

Thanks Rich


ntor offers reduced computational complexity for circuit setup compared to TAP. Tor circuits are setup one hop at a time with each link using TLS. Diffie-Hellman (DH) is the algorithm used for computing keys to be exchanged and is responsible for what we conceptually know as forward-secrecy.

Notable differences between TAP and ntor

Tor Authentication Protocol (TAP), the original/legacy handshake, will be used where ntor isn't supported.

  • Generating a DH key is computationally expensive
  • Need to generate DH public/private values, and perform exchange at each node, as the circuit is extended
  • DH Keys are encrypted/decrypted with RSA at each node using onion-key
  • An analysis of TAP can be found here

ntor is the handshake added in It will be used where consensus method is at least 16 and an ntor public key is available.

-- leeroy

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.