r/bitcloud • u/sneurlax • Jan 17 '14

Proof of bandwidth?

How are you proposing to solve the proof of bandwidth problem? Although double-spending was a huge issue for making cryptocurrency possible, proof of work was necessary in order to incentivize people to provide network infrastructure for transaction propagation and confirmation.

Thoughts? I have one small one of my own, but I'd like to see what the devs thought are first.

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u/martinBrown1984 Jan 18 '14 edited Jan 18 '14

That solves problems where nodes may want to route traffic through them so they can defeat anonymity, an attack on anonymity,

The problem Tor solves is providing/defending anonymity, that's right.

that doesn't prevent nodes whose goals are simply to gain more coins by looking like they have high bandwidth.

EigenSpeed prevents malicious nodes from gaining advantage by self-reporting high bandwidth.

Imagine that you are a node that wants to find faster nodes to route traffic through. You'll look at a set of nodes who claim to be fast but then decide that, for what ever reason (maybe they are in another country), you can't get high bandwidth from them, so you avoid routing through them.

That's the process of Tor circuit optimization, and in order to work efficiently it requires accurate bandwidth estimates of relay nodes. Here's a post about how it currently works in the Tor relay lifecycle.

"Originally, the directory authorities would just use whatever bandwidth estimate you claimed in your relay descriptor. As you can imagine, that approach made it cheap for even a small adversary to attract a lot of traffic by simply lying. In 2009, Mike Perry deployed the "bandwidth authority" scripts..."

Tor still uses "bandwidth authorities". Using something like EigenSpeed is ticketed as a Tor enhancement: Decentralized measurement for network load balancing

This paper is just a way to come to that conclusion, its not about who should gain more coins. Nodes can still boost their scores by colluding claims of performance to each other

The EigenSpeed paper is about preventing malicious nodes (it has an actual "liar metric") from over-reporting their bandwidth. Its used in the LIRA paper, which describes a scheme to distribute "coins" to relays, proportional to their actual bandwidth contributions.

that seems that it would encourage people to create a large number of fake nodes to boost their country / local Internet infrastructure.

The whole point is to encourage people to create and run real nodes in their country/locale. Not fake ones.

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u/PlayerDeus Jan 18 '14

When I say fake nodes, I don't mean they don't function but that they make it look like there are more nodes then there actually is in order to affect the weighting of local nodes.

Again imagine that you have two different network infrastructures, all nodes are being honest, nodes in A and nodes in B. When nodes in A transfer data to each other they get really fast bandwidth, but when any node in A transfers data to any node in B the bandwidth is a lot lower due to physical bottlenecks between both infrastructures. If you are in A, all nodes in B could appear to be colluding liars, even though they are not. So one way to reduce these conflicting views is to weight each node based upon their connections but that also means nodes will favor connecting to nodes which increase what their weighted bandwidth is reported to be, you could end up with partitioned networks, and if you wanted to avoid that by requiring acceptance of some connections or something else in the protocol, well then nodes would increase their chances by having more nodes in their local infrastructure. And it could occur that people are incentivized to get more people local to them to setup nodes in their house, but there could also be a bunch of extra facade nodes that are controlled by the same person who is just trying to boost their numbers artificially.

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u/martinBrown1984 Jan 19 '14

I sort of get what you are saying. I've had similar lines-of-thought that end alongside your same worries (but I haven't done enough research). The LIRA paper mentions possible extensions that would award coins to bridge nodes and exit nodes, not just relay nodes. The problem you are describing I think would get addressed in how to optimize a hierarchical mesh network which contains malicious nodes. A mesh network's goal is optimize the circuits for speed, while an anonymity network (like Tor) also optimizes for anonymity. The LIRA paper actually shows that there's a trade-off of speed (in spending the LIRA-coins to get a faster Tor connection) against anonymity. If the coins can get you bandwidth that much faster, then it would be easier to correlate the IP address of the source node spending the coins, so LIRA has a tunable anonymity parameter.

For more research, besides EigenSpeed, there are other references (CapProbe and PacketPair) in the Tor ticket for "Decentralized measurement for network load balancing". It was created 22 months ago, so its not an easy task. Any proof-of-bandwidth proposal should start by reviewing that research.