Date: Tue, 16 Jun 2020 05:23:01 +0000
To: ZmnSCPxj <ZmnSCPxj@protonmail.com>,
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Reply-To: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Message-ID: <_VqB84inr1oM8O9n4r1BZ_t7BPRFaJQ3ifZqnsLwFKNlQAKtPdwUFK825Wja0PTyllzLERlmiWWMLSiamYR83d7MXH3ERCON-u-IkH5R5XA=@protonmail.com>
In-Reply-To: <7BPgx65Eh5HE5wLIqeG9G-bdsxxkDJJIzcyOJvS6_FIxXfA10sbFe5dfwQDNiEOExZ9Y72lHq88lKzcBRIFnYGFY5I2vwk6Dg7BcCMjmS2Y=@protonmail.com>
References: <CALZpt+FqAWCAqCLF2HsajL84sOvst_X9_34bb_tvUxLFw=HTAA@mail.gmail.com>
 <7cWQJzkWNEZCI2fYYrJCFxrmGfDGFAtsOyGpXRmB-g4Qhm2jzhyxLtuOIpJAr2CMJjAjri12lmR-h96ev3NWqaTgDtc_NN0yhyVxuIlBuzU=@protonmail.com>
 <CALZpt+EsACbq1QM9MFkC63_gDXW0vHfeTjXc7C9r4+2-1WKAJw@mail.gmail.com>
 <m-yAKsQ52s-bYOrtEXVwETAcJ8sSbJt0k9WDN1ueidJ01IaEHRJtq9Odffmz_2utLxPfmI418x58aFc3vKBpOD2FKqgeCUAn1mvI1OSyGRY=@protonmail.com>
 <7BPgx65Eh5HE5wLIqeG9G-bdsxxkDJJIzcyOJvS6_FIxXfA10sbFe5dfwQDNiEOExZ9Y72lHq88lKzcBRIFnYGFY5I2vwk6Dg7BcCMjmS2Y=@protonmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Subject: Re: [bitcoin-dev] CoinPool,
	exploring generic payment pools for Fun and Privacy
Precedence: list

Good morning Antoine, Gleb, and list,

In some ways, CoinPool is really part of a swarm of ideas:

* CoinPool
* Multiparticipant (N > 2) channels
* Channel factories
* Nodelets

What CoinPool and multiparticipant channels buy us is better flexibility wi=
th forwarding.
For example, if we compare a multiparty channel to a channel factory, suppo=
se there exists three entities A, B, and C in the multiparty construction.

In a channel factory, each entity has to decide how much of its liquidity t=
o tie up in a channel with a specific other peer in the multiparty construc=
tion.
This limits the practical payment forwarding when integrated into the Light=
ning Network.

In a CoinPool, any of the entities can forward to any of the other entities=
, without tying their liquidity to a channel specifically with those entiti=
es.

However, in a CoinPool, once any of the entities goes offline, the entire C=
oinPool can no longer update.
This is in contrast with channel factories, where, if entity C goes offline=
, the channel between A and B remains useable for forwarding.
In other words, channel factories degrade gracefully.

Further, we already have a decent solution for liquidity redistribution: JI=
T Routing by Rene Pickhardt.
Thus the liquidity issue with channel factories are somewhat mitigated (and=
 if all participants are online, they also have the option of redistributin=
g channel funds *inside* the factory as well, not just JIT routing), while =
gaining graceful degradation of the factory.


Another is that pathfinding algorithms work best if graph edges are edges a=
nd not in fact some kind of twisted multi-edge that connects more than two =
nodes together.

On the other hand, the participants of a CoinPool could create a "virtual n=
ode" that is a MuSig of their individual keys, and report that as the "real=
" node on LN gossip (each of them pretending to have a large channel with t=
hat virtual node), so that the rest of the network only sees edges that lin=
k two nodes (and existing pathfinding algos still work seamlessly, never re=
alizing that this node is actually a virtual node that represents a CoinPoo=
l).
This is basically them creating a sort of Nodelet node, which other nodes c=
annot make channels to, and which uses channels with the Nodelet node as pr=
oxies for the CoinPool as a whole.


Regards,
ZmnSCPxj