From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id A8FEDC0051 for ; Mon, 21 Sep 2020 01:14:37 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 9247085F2F for ; Mon, 21 Sep 2020 01:14:37 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id pO0UUsKvaw0z for ; Mon, 21 Sep 2020 01:14:35 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail-40141.protonmail.ch (mail-40141.protonmail.ch [185.70.40.141]) by fraxinus.osuosl.org (Postfix) with ESMTPS id 68C1185F19 for ; Mon, 21 Sep 2020 01:14:35 +0000 (UTC) Date: Mon, 21 Sep 2020 01:14:29 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com; s=protonmail; t=1600650872; bh=PsFrAlXAcdRHMv4SE++TveZXYd8hhk26eta9hPH9dEg=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=iOkWlFFVF/eDRK2Uzcw+PobuSSMcagOeKKP1gKKftniVQbB22Q4LvQuqTi215MP8W btK8KpykLxUTgAeBdEvJMjCt7KxC8Rj7ZT0ZnAJt+hH3u7enGkVKuQRe6U4hWUVlxd xM6VjIMvQ2sPe1lNo6jqggSiWCL2XX3mQc80K+o0= To: Tom Trevethan From: ZmnSCPxj Reply-To: ZmnSCPxj Message-ID: In-Reply-To: References: <2Abk4Gqv5hJyGtA8Gg1WCP5RNuyUFkmRn1uUKp_mdUaXrRTz4SDBTPi0MGU7D5jj36VSzrqsIiO5lMR4gGRApRX2jyp8vXDeHBnFt-6ca-g=@protonmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: Bitcoin Protocol Discussion Subject: Re: [bitcoin-dev] Statechain coinswap: assigning blame for failure in a two-stage transfer protocol. X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 21 Sep 2020 01:14:37 -0000 Good morning Tom, > Hi ZmnSCPxj, > > Thanks for the reply.=C2=A0 > > > Okay, I suppose this is much too high-level a view, and I have no idea = what you mean by "statecoin" exactly. > > Sorry, most of the protocol details are in the links, but terminology sho= uld be made clearer. A=C2=A0"statecoin" is a UTXO that is a 2-of-2 between = the owner and SE (the tr*sted signing server) i.e. can be transferred off-c= hain.=C2=A0 > > Also, should have been clear that `addr1` is the 'statecoin=C2=A0address'= which is different from the on-chain address (the shared public key the bi= tcoin is paid to). The on-chain address does not change, whereas the=C2= =A0'statecoin=C2=A0address' changes with each new owner and is used to auth= enticate owners to the SE and act as proof of ownership on the=C2=A0statech= ain - it is not related to the onchain address/pubkey and controlled by the= owner only.=C2=A0 > > > So it seems to me that this requires tr\*st that the coordinator is not= going to collude with other participants. > > This is correct. The SE also must be trusted to not actively defraud user= s. The main advantage of this scheme is that assuming the SE can be trusted= , it is strictly non-custodial.=C2=A0 > > > This is strictly worse than say Wasabi, where the coordinator colluding= with other participants only allows the coordinator to break privacy, not = outright steal funds. > > It seems to me that the trust-minimized CoinSwap plan by belcher_ is su= perior to this, with reduced scope for theft. > > This is true if the overriding aim is trust minimisation, but not if the = aim is speed and cost while staying=C2=A0non-custodial. Off-chain SE transa= ctions are near instant and orders of magnitude cheaper than on-chain. Prob= ably best thought of as a non-custodial centralised mixer.=C2=A0 I think the entire point of non-custodiality ***is*** trust minimization. The main objection against custodiality is that someone else can prevent yo= u from spending the coin. If I have to tr\*st the SE to not steal the funds, is it *really* non-custo= dial, when after a swap, a corrupted SE can, in collusion with other partic= ipants, take control of the coin and prevent me from spending it as I wish? So I think touting "non-custodial" is relatively pointless if tr\*st is not= minimized. (I am aware there is an update mechanism, either Decker-Russell-Osuntokun o= r Decker-Wattenhofer, that is anchored off he onchain transaction output, b= ut anyone who can recover the raw keys for signing the funding transaction = output --- such as a previous participant and a corrupt SE --- can very eas= ily bypass the mechanism.) For example, in my previous description of [implementing investment aggrega= tion](https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2020-July/018= 055.html), while I admit you need tr\*st in the business owners who you are= investing in, it does not require tr\*st in the aggregator, due to the n-o= f-n, which cannot be reconstructed by the aggregator and all other particip= ants without you. Regards, ZmnSCPxj