teor teor2345@gmail.com writes:
On 16 Nov 2017, at 00:38, Alec Muffett alec.muffett@gmail.com wrote:
I think it's important to point out that a Tor client is never guaranteed to hold a *definitive* consensus.
That's why I say "(mostly) definitive" in my text - my feeling is that a locally-held copy of the consensus to be queried is going to be on average of far higher quality, completeness, and non-stagnancy than something that one tries to scrape out of Onionoo every 15 minutes.
Please don't use a consensus or a tor client to check for exits for this purpose. It produces significant numbers of false negatives, because some exits use other IP addresses for their exit traffic.
I'm actually not a fan of Alec's idea, and I agree with you that there will be a significant number of false negatives, but it might be worth pointing out that IIUC false negatives are probably not so damaging in this use case, because it would result in users getting thrown to the normal website instead of the onion site, because the website didn't realize they are Tor users. So not much damage done there.
False positives are a bit more damaging for reachability because it means that the website would throw normal users to the onion website which would fail, but that's not so likely (except if exit node operators surf from their exit node, or if an exit node IP is shared to other people).