Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 8AB33CF8 for ; Tue, 14 Aug 2018 18:34:50 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-oi0-f44.google.com (mail-oi0-f44.google.com [209.85.218.44]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 21FF6735 for ; Tue, 14 Aug 2018 18:34:50 +0000 (UTC) Received: by mail-oi0-f44.google.com with SMTP id b15-v6so35395465oib.10 for ; Tue, 14 Aug 2018 11:34:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lifewithalacrity-com.20150623.gappssmtp.com; s=20150623; h=mime-version:from:date:message-id:subject:to; bh=OAMH00fGDL+Y4OZ8QtHznKz7ww+4qqZhqXbk+VuOaCE=; b=2K9+m+nHHv1E6Mca/dn+94/50MnHFTk1BRakvT8oWmiWufDWTPQ5ehQV0Om1k/lH6a M7mdhuORyKk0RlIkblxv+/92PnxpDd4cHlK0R5dYAlKTNCHVttZCai0IBbj2DTACdBiD 5pqvSH9qd0nCynyNH7g0ANQG6iJJaruKh3DnSVg+6up43DX7HI2Pnih2OL8e0xWme3r4 dN3XDo1FNsqMGaLKMj4b4HpoqXeUAxEObBs7wpZ8PhmNoHNJK0O9EOeHvqauqc0Ka8i6 TWxJ6yip3iWv4XVbuIqau/gBghYlmQIiGuBJX/vrtB7jSuMAnD/ZBpna4N8chKanpBzI XH0w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to; bh=OAMH00fGDL+Y4OZ8QtHznKz7ww+4qqZhqXbk+VuOaCE=; b=O3ahKqnw+9Dgu1LDB86t9URF0VM+SP6XgSRikcFbwqwXjeO5k6hNfm8YmiWguYzNJc xpdMWXHCO1fjbM7jOQxq5MkkiDYvx+BE9FxxppxYf5hgj/G7b2t48Hd44yQ7LEWQVaLg lHSplPEwg0fVXyQAGHvlIfsZDdeq6ZzFsU2ggEDy8pC2iMOFPbNXjvdQZ0wkvTjSK4PU 6hgEypNmK0d9mMS44+ksUXH8i94+B+w4g4bZMwq5CTUGN7PgVRZLoir2ycRpix6k1532 F9g6A3wUCd8JdcEpZUVO9iHImaR1kkocdqLgm/9O25Eq0evCCvljSbnj2ppMqlSB1LgL b6PA== X-Gm-Message-State: AOUpUlGUsK2xSJ7MYlYLzk0akZNxDQivbNJ9AqDDX4BN2hBfq8LYcwNX SCDiRVznMkmFoUUJt1hYoOHJCIB29u2QltlZ7by48o1J X-Google-Smtp-Source: AA+uWPyMZifdsAXHkljMfafIwkxIc4OySxKtE/QxCo7cbVizRLsjnriEKNXLZC4miY++s9zkRvpMCXfZSD8ruBvb14k= X-Received: by 2002:aca:b3d6:: with SMTP id c205-v6mr25486825oif.133.1534271689095; Tue, 14 Aug 2018 11:34:49 -0700 (PDT) MIME-Version: 1.0 From: Christopher Allen Date: Tue, 14 Aug 2018 11:34:13 -0700 Message-ID: To: bitcoin-dev@lists.linuxfoundation.org Content-Type: multipart/alternative; boundary="00000000000004826105736977c3" X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, FREEMAIL_FROM, 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: Wed, 15 Aug 2018 13:28:40 +0000 Subject: Re: [bitcoin-dev] Claiming an OP_RETURN Prefix 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: Tue, 14 Aug 2018 18:34:50 -0000 --00000000000004826105736977c3 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On August 5, 2018 9:11:26 PM UTC, Lautaro Dragan via bitcoin-dev wrote: >Should we actually be using the BIP process to claim a prefix? I recommend against using an op_return prefix, as they allow for transaction censorship. In fact, in our case, where we use an IPFS hash in an op_return, we remove the IPFS multihash prefix information to post a =E2=80=9Cbare=E2=80=9D SHA2= 56 hash to look like many other hashes being posted in op_returns, to minimize any ability for a miner to identify our transaction. The more projects that do this the better =E2=80=94 a form of herd immunity. Longer term I=E2=80=99m looking for more responsible ways to publish this h= ash, for instance have the hash be in the witness script data, so that it can be easily purged from nodes that do not wish to preserve it and prevent block size bloat. However, to do so everyone has to do it the same way, ideally have it look like any other transaction. I=E2=80=99ve not quite seen a soli= d proposal for best practices here. =E2=80=94 Christopher Allen --00000000000004826105736977c3 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On August 5, 2018 9:11:26 PM UTC, Lautaro Dragan via bitco= in-dev <bitcoin-dev at list= s.linuxfoundation.org> wrote:
>Should we actually be using the= BIP process to claim a prefix?

I recommend against using an op_retu= rn prefix, as they allow for transaction censorship.

In = fact, in our case, where we use an IPFS hash in an op_return, we remove the= IPFS multihash prefix information to post a =E2=80=9Cbare=E2=80=9D SHA256 = hash to look like many other hashes being posted in op_returns, to minimize= any ability for a miner to identify our transaction. The more projects tha= t do this the better =E2=80=94 a form of herd immunity.

Longer term I=E2=80=99m looking for more responsible ways to publish = this hash, for instance have the hash be in the witness script data, so tha= t it can be easily purged from nodes that do not wish to preserve it and pr= event block size bloat. However, to do so everyone has to do it the same wa= y, ideally have it look like any other transaction. I=E2=80=99ve not quite = seen a solid proposal for best practices here.

=E2= =80=94 Christopher Allen
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