From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 2F7AAC016F for ; Tue, 12 May 2020 11:30:54 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id 14F6326016 for ; Tue, 12 May 2020 11:30:54 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id IEOLdEz3xxWv for ; Tue, 12 May 2020 11:30:52 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail-ed1-f48.google.com (mail-ed1-f48.google.com [209.85.208.48]) by silver.osuosl.org (Postfix) with ESMTPS id 63E9125D07 for ; Tue, 12 May 2020 11:30:52 +0000 (UTC) Received: by mail-ed1-f48.google.com with SMTP id b91so6578347edf.3 for ; Tue, 12 May 2020 04:30:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=TQt5MCyMJhZ2bPK3CkF4iRw0AnPbfF+mEpQ2pl26Fwo=; b=OpcrbsmqFV7bIWnDDx7TVO7iy04xtcxVAeqZIJU+9XYOB5drqdshlzxy5stzpA5hCI A3dgFLXp6PYvYZhitPrs9AodVpfhf1WawaNp224jm6uObcQNgf9tbyTomfPWTMnjNa8j 98J/x2Q/KN40X1g64XFWM/5Vb7drUnxDS2aQ3yE9g1ahPEgOAEkRfZbYOdZZfxgCcIng /EER5U6b5xIQwoChpisPljZTLsoyU8BXKBHPaXyC3Ggl78PO6Kan97VPs1MNjkADxoTO KzCnSHbyY6Wp6CEtD52/hMoqY1Ev+X9eP5vw3+czUefYuQ6ql0jqlureL8mwuN+gcdpL o5bA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=TQt5MCyMJhZ2bPK3CkF4iRw0AnPbfF+mEpQ2pl26Fwo=; b=XCJbafzeoKmKWC4fy2IBQX1DidE/sxLLPYd6EmAzht41jy0HCqHLNewShKvxbhZIzh l4pR+AI0lsJVljFy84wpEYxg4r57HRGiGMVteNvtTDOC42Y1ly20cjwu5Uv66GB9lxLz vi1OWX9SM8zwy5+obXYBvPshfSvgYrIIS9IAcltNWJaILQb/UKtfn/oyOQpNIm5aBOzf HI5hKeNI925ccDWQIk1bBw5VQVSCkPSYGVeYyF8FJ1HEmozb5DN39p6JvSQU+tCEB0Qn +S8LLM9XMPEbAgg0DjifnCLVhjzcxdNQRu/logAU8KlSvPQP9FF9sTqtXFOd8kDFKewY dVrQ== X-Gm-Message-State: AGi0Pubn1+0eiS1neXs/wcEUlMdqwBF87TOryTpIkYO0s0qbVkIg6EUW /wjpoVM9APUEqJaL5YamZGhAgfDXKslsuRxxI+TJzxMw X-Google-Smtp-Source: APiQypI4GQXdprOzL+TiXg5mw6mbA5i7sZ53gf5SShBX0VjkmbCbd1kVpjjZoRlv2Tx3q+UXGJSS80G9EJvwbiIg1x8= X-Received: by 2002:aa7:c499:: with SMTP id m25mr16741740edq.122.1589283050133; Tue, 12 May 2020 04:30:50 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Ruben Somsen Date: Tue, 12 May 2020 13:30:38 +0200 Message-ID: To: Bitcoin Protocol Discussion Content-Type: multipart/alternative; boundary="000000000000a69cb105a571cbf8" X-Mailman-Approved-At: Tue, 12 May 2020 11:35:10 +0000 Subject: Re: [bitcoin-dev] SAS: Succinct Atomic Swap 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: Tue, 12 May 2020 11:30:54 -0000 --000000000000a69cb105a571cbf8 Content-Type: text/plain; charset="UTF-8" Hi ZmnSCPxj, >Would this not work? I considered and rejected that model for the following reason: there are moments where both Alice and Bob can claim the BTC. If they both attempt to do so, it also reveals both secrets, causing the LTC to also be claimable by both parties. This chaotic scenario is a failure mode that did not seem acceptable to me. The revoke transaction was specifically added to mitigate that issue (invalidating any attempt of Bob to claim the coins and reveal his secret). That said, it doesn't particularly seem in either party's interest wait until a moment where two timelocks become valid, so maybe it is not quite as bad as I thought. However, it still means that the incompetence/malevolence of one party can lead to losses for both parties. I have my doubts a gain in privacy in the uncooperative case is worth that risk. Of course it also reverts the protocol to 3 transactions, instead of 2, but regardless, not having to watch the chain is probably more practical in many cases. As an aside, if both chains support timelocks then we can ensure that the more expensive chain only receives one transaction. >if relative locktimes are used as often as absolute locktimes for block-sniping-prevention and a decent Scriptless Script system, then all protocol aborts should be doable with no information leaks I see your point, interesting observation. >A sidenote as well, that if Alice typically uses an HD wallet, the UTXO on the LTC side would not be in that HD, and if Alice wants to cold-store the LTC, it should move the money as well into an HD pubkey. Agreed, I had that listed as one of the disadvantages: "Access to money is contingent on remembering secrets (backup complexity)" Cheers, Ruben On Tue, May 12, 2020 at 8:50 AM Lloyd Fournier wrote: > A quick correction to my post: > >> >> Here's where the truly novel part comes in. Ruben solves this by >> extending the standard *TLC contract: >> 1. Bob redeem with secret >> 2. Alice refund after T1 >> 3. Bob redeem without secret after T2 >> >> This is actually: > > 1. Bob redeem with redeem secret > 2. Alice refund after T1 with refund secret > 3. Bob redeem without secret after T2 > > The fact that Alice reveals a secret when she refunds is crucial. > > LL > --000000000000a69cb105a571cbf8 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi ZmnSCPxj,

>Would this not work?

I cons= idered and rejected that model for the following reason: there are moments = where both Alice and Bob can claim the BTC. If they both attempt to do so, = it also reveals both secrets, causing the LTC to also be claimable by both = parties. This chaotic scenario is a failure mode that did not seem acceptab= le to me. The revoke transaction was specifically added to mitigate that is= sue (invalidating any attempt of Bob to claim the coins and reveal his secr= et). That said, it doesn't particularly seem in either party's inte= rest wait until a moment where two timelocks become valid, so maybe it is n= ot quite as bad as I thought. However, it still means that the incompetence= /malevolence of one party can lead to losses for both parties. I have my do= ubts a gain in privacy in the uncooperative case is worth that risk.
Of course it also reverts the protocol to 3 transactions, instead of 2, bu= t regardless, not having to watch the chain is probably more practical in m= any cases. As an aside, if both chains support timelocks then we can ensure= that the more expensive chain only receives one transaction.

>if= relative locktimes are used as often as absolute locktimes for block-snipi= ng-prevention and a decent Scriptless Script system, then all protocol abor= ts should be doable with no information leaks

I see your point, inte= resting observation.

>A sidenote as well, that if Alice typically= uses an HD wallet, the UTXO on the LTC side would not be in that HD, and i= f Alice wants to cold-store the LTC, it should move the money as well into = an HD pubkey.

Agreed, I had that listed as one of the disadvantages:= "Access to money is contingent on remembering secrets (backup complex= ity)"

Cheers,
Ruben


On Tue, May = 12, 2020 at 8:50 AM Lloyd Fournier <lloyd.fourn@gmail.com> wrote:
A quick correct= ion to my post:

Here's where the truly novel part comes in. Ruben solves this by exte= nding the standard *TLC contract:
1. Bob redeem with secret
=
2. Alice refund after T1
3. Bob redeem without secret after = T2

This is actually:

1. Bob redeem with redeem secret
2. Alice re= fund after T1 with refund secret
3. Bob redeem without secret aft= er T2

The fact that Alice reveals a secret when sh= e refunds is crucial.

LL=C2=A0
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