On 26/03/14 16:54, Michael Rogers wrote: > Hi all, > > (Please let me know if this belongs on tor-talk instead of here.) > > I'm working on a messaging app that uses Tor hidden services to > provide unlinkability (from the point of view of a network observer) > between users and their contacts. Users know who their contacts are, > so we don't need mutual anonymity, just unlinkability. > > I wonder whether we need everything that the Tor hidden service > protocol provides, or whether we might be able to save some bandwidth > (for clients and the Tor network) and improve performance by using > parts of the hidden service protocol in a different way. > > First of all, we may not need to publish hidden service descriptors in > the HS directory, because we have a way for clients to exchange static > information such as HS public keys out-of-band. > > Second, we may not need to use introduction points to protect services > from DoS attacks - we can assume that users trust their contacts not > to DoS them. > > Third, we may be able to reduce the number of hops in the > client-service circuits, because we don't need mutual anonymity. > > This isn't the first app to use hidden services for unlinkability, so > I expect this topic's come up before. Are there any discussions I > should look at before coming up with hare-brained schemes to misuse > the hidden service protocol? > > Cheers, > Michael A further requirement, as I understand from a previous discussion with Michael, is that the app can't assume that each user has a publicly-accessible IP/port. One idea (instead of using HS) is to simply have each user also be a normal (non-hidden) internet service, and have the contact connect to them through Tor. However, this doesn't address the IP/port issue. We could look into ICE as a NAT traversal technique, but it's far from clear whether this will work *through* Tor (i.e. to have the exit node run ICE with the contact). So another possibility is using a HS-like system, where the rest of the network provides the listenable ports. X -- GPG: 4096R/1318EFAC5FBBDBCE git://github.com/infinity0/pubkeys.git
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