Add a transport that requests a proof of work to incoming connections if necessary

[tomaka]

In order to prevent a node from being flooded with incoming connections, we can request a proof of work from incoming nodes. The difficulty of the proof would be proportional to the number of nodes that are currently attempting connection.

A timeout would of course be required.

The details of this scheme may be a bit tricky and should be figured out.

In details, once a certain threshold has been reached, the listener would cease to support all protocols except for /libp2p/pow/1.0.0 (or a similar name). Once this protocol has been successfully negotiated and the PoW fulfilled, the dialer would request the actual protocol (eg. secio) on "top of it".

[CPerezz]

Is the goal to prevent DDOSing?
If so, there's an interesting paper on P2P networking kadkast which uses PoW for the ID generation which is at the same time tied to the external IP that you have (so that you can't pre-compute the PoW).

If it isn't, and it just wants to prevent overloading of the node, the first thing I would suggest for sure is to avoid any hashing algorithm that is GPU-highly optimizable since then it would become a mess to stablish a threshold to set as a minimum PoW required. I would suggest to use something like Poseidon or Pedersen hashes (which although they are optimizable, the difference it's not simply overwhelming as it happens with the SHA family).

I would be interested in discussing more about that and helping if this is a feature that's really desired in the lib!

[mxinden]

Hi @CPerezz,

Thanks for offering your help. Given that the initial proposal is quite dated, I don't think this is a feature that is really desired today. This of course should not stop you from making a proposal in case you are in need for such mechanism.