Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 966D228A6 for ; Fri, 19 Jul 2019 22:48:58 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-pl1-f182.google.com (mail-pl1-f182.google.com [209.85.214.182]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id EC8248B6 for ; Fri, 19 Jul 2019 22:48:55 +0000 (UTC) Received: by mail-pl1-f182.google.com with SMTP id c2so16249827plz.13 for ; Fri, 19 Jul 2019 15:48:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=woobling.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=jY0gzjcQy5tpp3BeWgQ99NfmNRgjS6/nzQ/97RrBkEI=; b=YBz/uf+O1ym/dyZ/+LSM12edlelFDqNHr8N/Md7xZWOYHxjivx223oPxKuyW2Ad2oK yFUo5UiAMgCSCcp/OXdHdvqUGHJ/KIASmRJAoKM/N++yJArZwtrK/ScdzM9VFN6d/GKv e/R6t+caRD5QT5ZHv+e2zdlvjtS57u3yEsGWY= 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; bh=jY0gzjcQy5tpp3BeWgQ99NfmNRgjS6/nzQ/97RrBkEI=; b=cZ4PrtY5k9YVQkKGBOXHdu5MvFzrPaaPaPzDvFrm1bcZmqukllGnH65oFa7MUwibIn pj9RIJmUxxlkT3WXw0omQ4+t8YaOK1/2TLZg/oJB0aeusL/fNVKnY+z5wJlPXWpyreMm ib2kxUroSIHvFC13q122dYzfTm5xfx5l7vUBipwpz/GJGvB7mfP220ZetNo93Cm5VSwD 32DSuGPxTDWzSbM4OAipMspFYNZ1ut9jUq+gh1W58pujMTaydiH6svfeLHExV4Iw/+J4 zAt9ZFnkCLyWZSwL4a9YPqWjoWGhBjsCA7KW21HUAjdpOpx2HGz9DuMAgNSpRK/lyGmr YGWg== X-Gm-Message-State: APjAAAVaX2u/bb/9954l+wWkf6SmSIETMbxIx+KA8dVEfILKCfaF3Reu VrqntdlUq3eDofhj4CmKmy8B9pjpf5DVtP8ncMRXRNFz X-Google-Smtp-Source: APXvYqyz7MlHYDLqPbsGOlV96lAumT5yc4v/kugmj5fzdaA8WRF3wZnTQNx1sRd1VugCg0JTtY/2gAJTKvqSzqjc5yA= X-Received: by 2002:a17:902:9f8e:: with SMTP id g14mr13581707plq.67.1563576535503; Fri, 19 Jul 2019 15:48:55 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Yuval Kogman Date: Fri, 19 Jul 2019 22:48:43 +0000 Message-ID: To: Mike Brooks , bitcoin-dev Content-Type: multipart/alternative; boundary="000000000000fa678d058e108733" X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HTML_MESSAGE, RCVD_IN_DNSWL_NONE 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, 20 Jul 2019 03:24:33 +0000 Subject: Re: [bitcoin-dev] PubRef - Script OP Code For Public Data References 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, 19 Jul 2019 22:48:58 -0000 --000000000000fa678d058e108733 Content-Type: text/plain; charset="UTF-8" Hi, On Fri, 19 Jul 2019 at 17:49, Mike Brooks wrote: > Users will adopt whatever the client accepts - this feature would be > transparent. > My skepticism was based in an assumption on my part that most such data is produced by actors with a track record of neglecting transaction efficiency. I'd be happy to be proven wrong, but considering say usage rates of native witness outputs, or the fraction of transactions with more than 2 outputs so far I see little evidence in support of widespread adoption of cost saving measures. Assuming this is intended as a new script version, all fully validating nodes need to commit to keeping all data indefinitely before they can enforce the rules that make transactions benefiting from this opcode safe to broadcast. That said, if successful, the main concern is still that of address reuse - currently there is no incentive in the protocol to do that, and with BIP32 wallets fewer reasons to do it as well, but this proposal introduces such an incentive for users which would otherwise generate new addresses (disregarding the ones that already reuse addresses anyway), and this is problematic for privacy and fungibility. Since address reuse has privacy concerns, I think it's important to draw a distinction between clients accepting and producing such transactions, if the latter were done transparently that would be very concerning IMO, and even the former would not be transparent for users who run currently pruning nodes. I'm not sure how an O(1) time complexity leads to DoS, that seems like a > very creative jump. > For what it's worth, that was in reference to hypothetical deduplication only at the p2p layer, similar to compact blocks, but on further reflection I'd like to retract that, as since both scenarios which I had in mind seem easily mitigated. Based on this response, it makes me want to calculate the savings, what > if it was a staggering reduction in the tree size? > Assuming past address reuse rates are predictive this only places an upper bound on the potential size savings, so personally I would not find that very compelling. Even if the realized size savings would be substantial, I'm not convinced the benefits outweigh the downsides (increased validation costs, monotonically growing unprunable data, and direct incentive for address reuse), especially when compared to other methods/proposals that can reduce on chain footprint generally improve privacy while reducing validation costs for others (e.g. batching, lightning, MAST for sufficiently large scripts, Schnorr signatures (musig, adaptor signatures), {tap,graft}root, ). Regards, Yuval --000000000000fa678d058e108733 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi,

On Fri, 19 Jul 2019 at 17:49, Mike Brook= s <m@ib.tc> wrote:
Users will adopt w= hatever the client accepts - this feature would be transparent.=C2=A0

My=20 skepticism was based in an assumption on my part that most such data is pro= duced by actors with a track record of neglecting transaction efficiency. I= 'd be happy to be proven wrong, but considering say usage rates of nati= ve witness outputs, or the fraction of transactions with more than 2 output= s so far I see little evidence in support of widespread adoption of cost sa= ving measures. Assuming this is intended as a new script version, all fully= validating nodes need to commit to keeping all data indefinitely before th= ey can enforce the rules that make transactions benefiting from this opcode= safe to broadcast.

That said, if successful, the main concern is still that of a= ddress reuse - currently there is no incentive in the protocol to do that, = and with BIP32 wallets fewer reasons to do it as well, but this proposal in= troduces such an incentive for users which would otherwise generate new add= resses (disregarding the ones that already reuse addresses anyway), and thi= s is problematic for privacy and fungibility.

Since address reuse has privacy= concerns, I think it's important to draw a distinction between clients= accepting and producing such transactions, if the latter were done transpa= rently that would be very concerning IMO, and even the former would not be = transparent for users who run currently pruning nodes.

=
I'm = not sure how an O(1) time complexity leads to DoS, that seems like a very c= reative jump.

F= or what it's worth, that was in reference to hypothetical deduplication= only at the p2p layer, similar to compact blocks, but on further reflectio= n I'd like to retract that, as since both scenarios which I had in mind= seem easily mitigated.

=C2=A0 Based on this response, it makes me want to calculate = the savings, what if it was a staggering reduction in the tree size?
<= /blockquote>

Assuming past address reuse rates are predictive this only places an uppe= r bound on the potential size savings, so personally I would not find that = very compelling. Even if the realized size savings would be substantial, I&= #39;m not convinced the benefits outweigh the downsides (increased validati= on costs, monotonically growing unprunable data, and direct incentive for a= ddress reuse), especially when compared to other methods/proposals that can= reduce on chain footprint generally improve privacy while reducing validat= ion costs for others (e.g. batching, lightning, MAST for sufficiently large= scripts, Schnorr signatures (musig, adaptor signatures), {tap,graft}root, = ).

Regards,
Yuval
<= /div>
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