[Lightning-dev] On Path Privacy

ZmnSCPxj ZmnSCPxj at protonmail.com
Sun Dec 29 11:14:58 UTC 2019

Good morning list,

> Unpublished Channels Delenda Est
> -----------------------------------

Further thoughts on this topic.

In blockchain layer, decentralization is not a value in and of itself.
Instead, it is an instrumental goal, with the terminal values actually being Censorship Resistance and Monetary Policy Preservation.
(i.e. the point of decentralizing is to prevent transactions from being labelled "illegal" and disallowed, and to prevent breaching of the pre-determined 21M limit)

Thus, we should consider as well that on the Lightning layer, decentralization is not a value in and of itself.
Again, we should consider what terminal value is actually being supported if we target decentralization in the Lightning layer.

I would like to refer to the original Peter Todd hub-and-spoke model, where in a single server (hub) is used by multiple clients (spokes) to send offchain payments to one another.
Obviously this has no privacy from the single server, as the single server now knows exactly who pays and is paid for all transactions (though xref. Chaumian techniques such as TumbleBit).

By allowing multiple hubs, we get a little more privacy, as a cross-hub payment requires that multiple hubs cooperate to identify the ultimate sender and ultimate receiver of the payment.
Still, with unpublished channels connecting "hubs" to "spokes", this allows such cooperation to be done and to properly identify every sender and receiver of every payment that goes through the cooperating parties.

To further increase privacy we truly need to destroy the separation of "hub" and "spoke".
To me, this is a form of decentralization, where there is no "server" and "client", but all nodes are equal peers.

Obviously not all nodes can be purely equal, as some nodes will have more liquidity available to them as an inherent part of the inequality of the universe.
The point is not to eliminate all inequality, but to reduce it to the minimum feasible, in order to promote certain properties, in this case, the valued Privacy Preservation.

* We should encourage people to at least increase the number of channels they have to the network.
  Multipath helps with this.
* We should discourage people from using completely unpublished channels, as this creates a (arguably not necessary) split between "hub" and "spoke".

Admittedly the goal may be too difficult in any case.


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