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Comment by stingraycharles | Hacker News Reader

Could someone elaborate on what potential threat is addressed here for the users? As far as I understand, a hidden service’s main purpose is to protect the privacy of the domain operator (in this case, Twitter).

For a user, however, just the act of connecting through Tor will protect their privacy (to a debatable degree). At the very least, it will circumvent any blocks put in place by their ISP and/or upstream.

What’s the advantage of a hidden service then?

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Alec Muffet, who helped Twitter on this, replied to your question on his blog: Why offer an Onion Address rather than just encourage browsing-over-Tor? [0]

[0] https://alecmuffett.com/article/16007

> Using onion services mitigates attacks that can be executed by possibly-malicious “Tor Exit Nodes” — which, though rare, are not nonexistent.

Would it make sense to be able to select your Tor exit node, in this case from a bunch offered by Twitter?

Then you'd have to trust these Twitter run exit nodes to not attack your traffic towards non twitter sites.

Exit nodes run by Twitter sounds less scary than exit nodes run by random folks.

Isn't this effectively same as dedicated .onion address?

That reduces your anonymity almost to the point of being useless. It means that any middle node connecting to a "Twitter" exit node would know you're almost certainly connecting to Twitter (effectively making the three-hop Tor circuit a two-hop circuit). In addition, Tor uses long-term guard nodes (the first hop) in order to defend against certain attacks. This means that the middle node could make a guess about what bucket a user is in based on the guard node. It's not as bad as not using Tor at all, but it gives middle relay nodes far more information than they normally would have -- and middle relay nodes are the easiest kind of node to set up.

The main reason why Tor has strong privacy guarantees is because every piece of traffic looks like every other piece of traffic. Changing what paths you pick based on where you're going undermines that in a fundamental way.

A major practical advantage is that Tor exit nodes regularly have their IP addresses marked as abusive and then you have to do a million captchas to sign in, and the onion service doesn't do that.

Another reason I can think of is that as more and more "legitimate" traffic moves onto Tor internal (no exit nodes) it becomes increasingly non-viable for nation states to execute a blanket ban on Tor traffic as it would be too disruptive to people and the economy.

IIRC With an onion site you don't need an exit node to visit the site.

So all traffic stays within TOR.

This. Result: The website (here Twitter) load faster, because Exit nodes are sometimes not that fast.

Perhaps an ignorant question, but don't hidden services not need exit nodes? It'd make using Twitter a lot faster, I'd assume?

Traffic to hidden services stays within the tor network so you don't need exit nodes. However it isn't necessarily faster. As I understand it, with a typical hidden service, the hidden service nominates certain nodes for clients to use to make contact with it and the client and the service build tor circuits to those nodes thereby preserving the privacy of both clients and servers but you end up with longer circuits than those to exit nodes, and you are limited by the slowest node in that chain. There is a mode for hidden services where you don't care about staying hidden (say you are twitter or the NYT running a service and everyone already knows who owns the site and where the datacenters are) where, as I understand it, you allow clients to build circuits directly to you which preserves client privacy but not server. This is more performant than a normal hidden service but I wouldn't call it fast.

Another benefit is that exit nodes tend to be saturated with traffic from folks using them to transit traffic onto the clearnet. As such, latency and throughput through these exit nodes is going to be pretty bad. Using Tor to directly view Twitter means that you aren't bottlenecked around an exit node to reach Twitter.

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