Return-Path: <ZmnSCPxj@protonmail.com>
Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137])
 by lists.linuxfoundation.org (Postfix) with ESMTP id BA900C000D
 for <bitcoin-dev@lists.linuxfoundation.org>;
 Tue, 21 Sep 2021 02:11:56 +0000 (UTC)
Received: from localhost (localhost [127.0.0.1])
 by smtp4.osuosl.org (Postfix) with ESMTP id AAD3940333
 for <bitcoin-dev@lists.linuxfoundation.org>;
 Tue, 21 Sep 2021 02:11:56 +0000 (UTC)
X-Virus-Scanned: amavisd-new at osuosl.org
X-Spam-Flag: NO
X-Spam-Score: 1.099
X-Spam-Level: *
X-Spam-Status: No, score=1.099 tagged_above=-999 required=5
 tests=[BAYES_50=0.8, DKIM_SIGNED=0.1, DKIM_VALID=-0.1,
 DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001,
 FROM_LOCAL_NOVOWEL=0.5, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001]
 autolearn=unavailable autolearn_force=no
Authentication-Results: smtp4.osuosl.org (amavisd-new);
 dkim=pass (1024-bit key) header.d=protonmail.com
Received: from smtp4.osuosl.org ([127.0.0.1])
 by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024)
 with ESMTP id dI45qLhffYn3
 for <bitcoin-dev@lists.linuxfoundation.org>;
 Tue, 21 Sep 2021 02:11:53 +0000 (UTC)
X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0
Received: from mail4.protonmail.ch (mail4.protonmail.ch [185.70.40.27])
 by smtp4.osuosl.org (Postfix) with ESMTPS id 73B6F40330
 for <bitcoin-dev@lists.linuxfoundation.org>;
 Tue, 21 Sep 2021 02:11:53 +0000 (UTC)
Date: Tue, 21 Sep 2021 02:11:42 +0000
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com;
 s=protonmail; t=1632190310;
 bh=YcWLYwU1MgvCIGiOpFuggt09qWVNasrRJJdc7gOcxCA=;
 h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From;
 b=I+yng9UnKZC8Em80tkybb2n9C/y0fWjUkGAh6UozlBdcLgjRMjbyFXcPTVRKObCjR
 R01l9XA/C/XopKYrYNwzOk+P1Mdlr48ezc5tL/Bqjndln4EMBEAmOobKupGmtnDFFx
 JiyHwd9S6ssoq/x4DTLZ24Thh7E2sD7L0xtREYy4=
To: Jeremy <jlrubin@mit.edu>
From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Reply-To: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Message-ID: <wDdSrhoOhFv2L7-IsDteE5PoDaZJk3aFZSvNgYd_PbuoVwLQ3qwheW-00wV52utUrpDhzsbAKvzYRhm5WUkXBtC-y0YPe9t17TaWodK1WsY=@protonmail.com>
In-Reply-To: <CAD5xwhh-1zUbPgYW6hE8q3CmhFZFdEqjx5pB7+VFM4mV=1FfaQ@mail.gmail.com>
References: <CAD5xwhh-1zUbPgYW6hE8q3CmhFZFdEqjx5pB7+VFM4mV=1FfaQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Cc: Bitcoin development mailing list <bitcoin-dev@lists.linuxfoundation.org>,
 lightning-dev <lightning-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] [Lightning-dev] Inherited IDs - A safer,
	more powerful alternative to BIP-118 (ANYPREVOUT) for scaling
	Bitcoin
X-BeenThere: bitcoin-dev@lists.linuxfoundation.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: Bitcoin Protocol Discussion <bitcoin-dev.lists.linuxfoundation.org>
List-Unsubscribe: <https://lists.linuxfoundation.org/mailman/options/bitcoin-dev>, 
 <mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=unsubscribe>
List-Archive: <http://lists.linuxfoundation.org/pipermail/bitcoin-dev/>
List-Post: <mailto:bitcoin-dev@lists.linuxfoundation.org>
List-Help: <mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=help>
List-Subscribe: <https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev>, 
 <mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=subscribe>
X-List-Received-Date: Tue, 21 Sep 2021 02:11:56 -0000

Good morning John Law,


> (at the expense of requiring an on-chain transaction to update
> the set of channels created by the factory).

Hmmm this kind of loses the point of a factory?
By my understanding, the point is that the set of channels can be changed *=
without* an onchain transaction.

Otherwise, it seems to me that factories with this "expense of requiring an=
 on-chain transaction" can be created, today, without even Taproot:

* The funding transaction output pays to a simple n-of-n.
* The above n-of-n is spent by an *offchain* transaction that splits the fu=
nds to the current set of channels.
* To change the set of channels, the participants perform this ritual:
  * Create, but do not sign, an alternate transaction that spends the above=
 n-of-n to a new n-of-n with the same participants (possibly with tweaked k=
eys).
  * Create and sign, but do not broadcast, a transaction that spends the ab=
ove alternate n-of-n output and splits it to the new set of channels.
  * Sign the alternate transaction and broadcast it, this is the on-chain t=
ransaction needed to update the set of channels.

The above works today without changes to Bitcoin, and even without Taproot =
(though for large N the witness size does become fairly large without Tapro=
ot).

The above is really just a "no updates" factory that cuts through its closi=
ng transaction with the opening of a new factory.

Regards,
ZmnSCPxj