Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 1AAF3FC3 for ; Fri, 24 May 2019 21:15:22 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 5E0ADF4 for ; Fri, 24 May 2019 21:15:21 +0000 (UTC) Received: from mail-ed1-f49.google.com (mail-ed1-f49.google.com [209.85.208.49]) (authenticated bits=0) (User authenticated as jlrubin@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id x4OLFIEv030252 (version=TLSv1/SSLv3 cipher=AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 24 May 2019 17:15:19 -0400 Received: by mail-ed1-f49.google.com with SMTP id b8so16068654edm.11 for ; Fri, 24 May 2019 14:15:19 -0700 (PDT) X-Gm-Message-State: APjAAAVvqckTz8WHaS2rG9X1h5LQp9/otW1ZtFUDBSBN4BXgb2Gmn9bQ zO1DvK4bukg7EUPoIjUJYvOrtlGiq/43rwuASuE= X-Google-Smtp-Source: APXvYqy3k5dsHl13jZf+tRgJs+BQwd68pw48yAxdEGHqjb8BjeH3LmhM1sATXiiDtfyIE1jGP/60vkSC5q5I3/L4dxM= X-Received: by 2002:a50:b662:: with SMTP id c31mr108977040ede.252.1558732518531; Fri, 24 May 2019 14:15:18 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Jeremy Date: Fri, 24 May 2019 14:15:07 -0700 X-Gmail-Original-Message-ID: Message-ID: To: ZmnSCPxj Content-Type: multipart/alternative; boundary="00000000000011286a0589a8b28e" X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,HTML_MESSAGE, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org X-Mailman-Approved-At: Sat, 25 May 2019 12:07:05 +0000 Cc: Bitcoin Protocol Discussion Subject: Re: [bitcoin-dev] Congestion Control via OP_CHECKOUTPUTSHASHVERIFY proposal X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 24 May 2019 21:15:22 -0000 --00000000000011286a0589a8b28e Content-Type: text/plain; charset="UTF-8" ZmnSCIPxj, I think you're missing the general point, so I'm just going to respond to one point to see if that helps your understanding of why OP_COSHV is better than just pre-signed. The reason why MuSig and other distributed signing solutions are not acceptable for this case is they all require interaction for guarantee of payout. In contrast, I can use a OP_COSHV Taproot key to request a withdrawal from an exchange which some time later pays out to a lot of people, rather than having to withdraw multiple times and then pay. The exchange doesn't have to know this is what I did. They also don't have to tell me the exact inputs they'll spend to me or if I'm batched or not (batching largely incompatible with pre-signing unless anyprevout) The exchange can take my withdrawal request and aggregate it to other payees into a tree as well, without requiring permission from the recipients. They can also -- without my permission -- make the payment not directly into me, but into a payment channel between me and the exchange, allowing me to undo the withdrawal by routing money back to the exchange over lightning. The exchange can take some inbound payments to their hot wallet and move them into cold storage with pre-set spending paths. They don't need to use ephemeral keys (how was that entropy created?) nor do they need to bring on their cold storage keys to pre-sign the spending paths. None of this really works well with just pre-signing because you need to ask for permission first in order to do these operations, but with OP_COSHV you can, just as the payer without talking to anyone else, or just as the recipient commit your funds to a complex txn structure. Lastly, think about this in terms of DoS. You have a set of N users who request a payment. You build the tree, collect signatures, and then at the LAST step of building the tree, one user drops out. You restart, excluding that user. Then a different user drops. Meanwhile you've had to keep your funds locked up to guarantee those inputs for the txn when it finalizes. In contrast, once you receive the requests with OP_COSHV, there's nothing else to do. You just issue the transaction and move on. Does that make sense as to why a user would prefer this, even if there is an emulation with pre-signed txns? --00000000000011286a0589a8b28e Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
ZmnSCIPxj,

I think you're missing the general point, so I'm just going to res= pond to one point to see if that helps your understanding of why OP_COSHV i= s better than just pre-signed.

The reason why MuSig and oth= er distributed signing solutions are not acceptable for this case is they a= ll require interaction for guarantee of payout.

In contrast, I = can use a OP_COSHV Taproot key to request a withdrawal from an exchange whi= ch some time later pays out to a lot of people, rather than having to withd= raw multiple times and then pay. The exchange doesn't have to know this= is what I did. They also don't have to tell me the exact inputs they&#= 39;ll spend to me or if I'm batched or not (batching largely incompatib= le with pre-signing unless anyprevout)

The exchange can tak= e my withdrawal request and aggregate it to other payees into a tree as wel= l, without requiring permission from the recipients.

They can a= lso -- without my permission -- make the payment not directly into me, but = into a payment channel between me and the exchange, allowing me to undo the= withdrawal by routing money back to the exchange over lightning.
=

The exchange can take some inbound payments to their hot wallet and = move them into cold storage with pre-set spending paths. They don't nee= d to use ephemeral keys (how was that entropy created?) nor do they need to= bring on their cold storage keys to pre-sign the spending paths.
=

None of this really works well with just pre-signing because you nee= d to ask for permission first in order to do these operations, but with OP_= COSHV you can, just as the payer without talking to anyone else, or just as= the recipient commit your funds to a complex txn structure.

La= stly, think about this in terms of DoS. You have a set of N users who reque= st a payment. You build the tree, collect signatures, and then at the LAST = step of building the tree, one user drops out. You restart, excluding that = user. Then a different user drops. Meanwhile you've had to keep your fu= nds locked up to guarantee those inputs for the txn when it finalizes.
<= /div>

In contrast, once you receive the requests with OP_COSHV, there= 's nothing else to do. You just issue the transaction and move on.


Does that make sense = as to why a user would prefer this, even if there is an emulation with pre-= signed txns?
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