[tor-talk] Guard Selection

Kevin Gallagher kcg295 at nyu.edu
Fri Feb 24 22:07:00 UTC 2017

Hello everyone,

I've read through the path selection specification document and I am a
bit confused about guard selection. It says that (when guard nodes are
enabled) "Tor maintains an ordered list of entry nodes as one's chosen
guards and stores the list persistently to disk. If a guard node becomes
unusable, rather than replacing it, Tor adds new guards to the end of
the list. When choosing the first hop of a circuit, Tor chooses at
random from among the first 3 (by default) usable guard on the list."

How is this list derived? What is it ordered by? How many guards are in
this list? Are guards added to the list with probability proportional to
their bandwidth, as with other types of node selection? Am I safe in
assuming that this is a local list unique to the client?

Sorry if these questions are a bit basic or if I missed the answers
elsewhere. Thanks for your time!


Kevin Gallagher
PhD Candidate, Department of Computer Science
New York University Tandon School of Engineering
2 MetroTech Center, 10th Floor
Brooklyn, NY 11201
Email: kevin.gallagher at nyu.edu
Key Fingerprint: D02B 25CB 0F7D E276 06C3  BF08 53E4 C50F 8247 4861

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