(micro)payments for anonymous routing in Tor?

[Josh Albrecht]

>     I have to comment here that all of the foregoing discussion gives me
> the impression that implementing such a system would add considerable
> overhead to the tor network.  If people are complaining about slowness
> now, then why would anyone want to add to the overhead?  The total
> throughput of the tor network would not be increased by a priority system,
> and it's conceivable that it might be decreased a bit due to the extra
> overhead, especially where that overhead incurs extra network traffic.

The network overhead is pretty small.  Payments are only sent every N
packets, not every packet, and the number of extra bits needed for the
coins is not excessive.  It's possible as you say that the total
throughput might not be increased by this incentive scheme, but I
think that is unlikely. More people would probably run relays if they
got something in return (whether that is money or faster access, which
are sort of interchangeable here)

> uniformly distributed.  Servers with published peak data rates
> greater than, for example, 4,000 KB/s are very few in number.  Such a "paid"
> system would essentially guarantee that the traffic of operators of those
> servers would have a high priority all the time because they would be unlikely
> ever to use much of their accumulated credit.  That means those folks could
> download huge files, always at a high priority, which might make their traffic
> more identifiable as being possibly/probably their traffic.

Actually, I think that the issues of reduced anonymity/higher speed
and whether you run a relay or not are directly related.  Nothing
forces a relay operator to use the faster bandwidth that is
accumulated by his relay if there is a fear that it will make him less
anonymous.  Alternatively, he might wish to take it out in the form of
a monetary payment (instead of faster service).  Similarly, a client
could get super fast access by paying, and so the partitioning
actually breaks the set of users into those going for speed, and those
striving for more anonymity (as opposed to clients vs server
operators).

However, you are right that, depending on how this was implemented, it
could partition the network into fast/slow user sets that might make
it easier for some attacks.

>     Frankly, at this point I don't think such a system of "payment" for
> relay priority is worth the cost in either development time and effort or
> anonymity and prospective user discouragement.  Many of the people in this
> world who have the greatest need for the benefits of a system like tor are
> also the people least likely to be able to run a relay without fear of
> harassment or worse from the states that rule them.

I think that people would contribute unpaid bandwidth to the network
for the same reason that they do now (altruism), especially if it were
the default setting (how many people really change the defaults?).
However, I see the incentives (bandwidth/monetary) as important to get
lots more people using Tor in the first place, which would hopefully
increase the total amount of free/unpaid bandwidth available through
the network.

>     The tor developers have, I believe, far more urgent matters to deal
> with than creating a priority system, and I don't think any priority system
> design has yet been shown not to have potential negative effects on the tor
> community.

I agree 100%.  I'm not at all proposing that the developers add this
in to Tor, they definitely have more important things to be working on
right now.  But I think that this kind of work is important for
further into the future--incentives (whether they are monetary or
performance-related) are going to be crucial to scaling the Tor
network.  And scaling the network is important for everyone's
security.  Without wide adoption of Tor, there are a lot of attacks
that are very easy against the network, and the lack of public
understanding and recognition makes it more likely that Tor could
suddenly become illegal in more and more countries.  So, I just think
that scaling is going to be very important, and we should be thinking
about what that will entail now, so that we can start thinking and
planning for it.

Thanks for the comments everyone.

 - Josh

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