Subject: Re: [bitcoin-dev] [Lightning-dev] On the scalability issues of onboarding millions of LN mobile clients

From: ZmnSCPxj <[email-masked]>
Date: Tue, 05 May 2020 13:49:58 +0000

Good morning ariard and luke-jr

> > Trust-minimization of Bitcoin security model has always relied first and
> > above on running a full-node. This current paradigm may be shifted by LN
> > where fast, affordable, confidential, censorship-resistant payment services
> > may attract a lot of adoption without users running a full-node.
>
> No, it cannot be shifted. This would compromise Bitcoin itself, which for
> security depends on the assumption that a supermajority of the economy is
> verifying their incoming transactions using their own full node.
>
> The past few years has seen severe regressions in this area, to the point
> where Bitcoin's future seems quite bleak. Without serious improvements to the
> full node ratio, Bitcoin is likely to fail.
>
> Therefore, all efforts to improve the "full node-less" experience are harmful,
> and should be actively avoided. BIP 157 improves privacy of fn-less usage,
> while providing no real benefits to full node users (compared to more
> efficient protocols like Stratum/Electrum).
>
> For this reason, myself and a few others oppose merging support for BIP 157 in
> Core.

BIP 157 can be implemented as a separate daemon that processes the blocks downloaded by an attached `bitcoind`, i.e. what Wasabi does.

The intention, as I understood it, of putting BIP157 directly into bitcoind was to essentially force all `bitcoind` users to possibly service BIP157 clients, in the hope that a BIP157 client can contact any arbitrary fullnode to get BIP157 service.
This is supposed to improve to the situation relative to e.g. Electrum, where there are far fewer Electrum servers than fullnodes.

Of course, as ariard computes, deploying BIP157 could lead to an effective DDoS on the fullnode network if a large number of BIP157 clients arise.
Though maybe this will not occur very fast?  We hope?

It seems to me that the thing that *could* be done would be to have watchtowers provide light-client services, since that seems to be the major business model of watchtowers, as suggested by ariard as well.
This is still less than ideal, but maybe is better than nothing.

Regards,
ZmnSCPxj