Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1YOrbr-0008Dt-PM for bitcoin-development@lists.sourceforge.net; Fri, 20 Feb 2015 17:43:27 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.212.179 as permitted sender) client-ip=209.85.212.179; envelope-from=mh.in.england@gmail.com; helo=mail-wi0-f179.google.com; Received: from mail-wi0-f179.google.com ([209.85.212.179]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1YOrbq-0008Q4-Nw for bitcoin-development@lists.sourceforge.net; Fri, 20 Feb 2015 17:43:27 +0000 Received: by mail-wi0-f179.google.com with SMTP id hi2so4550755wib.0 for ; Fri, 20 Feb 2015 09:43:20 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.180.78.4 with SMTP id x4mr26794054wiw.86.1424454200650; Fri, 20 Feb 2015 09:43:20 -0800 (PST) Sender: mh.in.england@gmail.com Received: by 10.194.188.11 with HTTP; Fri, 20 Feb 2015 09:43:20 -0800 (PST) In-Reply-To: References: Date: Fri, 20 Feb 2015 18:43:20 +0100 X-Google-Sender-Auth: rLpeAZdiiOzjobZ-YENKdJc3L5M Message-ID: From: Mike Hearn To: Adam Back Content-Type: multipart/alternative; boundary=f46d043bdf5ea0ef9f050f8896f4 X-Spam-Score: -0.5 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (mh.in.england[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 1.0 HTML_MESSAGE BODY: HTML included in message 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-Headers-End: 1YOrbq-0008Q4-Nw Cc: Bitcoin Dev Subject: Re: [Bitcoin-development] bloom filtering, privacy X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 20 Feb 2015 17:43:27 -0000 --f46d043bdf5ea0ef9f050f8896f4 Content-Type: text/plain; charset=UTF-8 Ah, I see, I didn't catch that this scheme relies on UTXO commitments (presumably with Mark's PATRICIA tree system?). If you're doing a binary search over block contents then does that imply multiple protocol round trips per synced block? I'm still having trouble visualising how this works. Perhaps you could write down an example run for me. How does it interact with the need to download chains rather than individual transactions, and do so without round-tripping to the remote node for each block? Bloom filtering currently pulls down blocks in batches without much client/server interaction and that is useful for performance. Like I said, I'd rather just junk the whole notion of chain scanning and get to a point where clients are only syncing headers. If nodes were calculating a script->(outpoint, merkle branch) map in LevelDB and allowing range queries over it, then you could quickly pull down relevant UTXOs along with the paths that indicated they did at one point exist. Nodes can still withhold evidence that those outputs were spent, but the same is true today and in practice this doesn't seem to be an issue. The primary advantage of that approach is it does not require a change to the consensus rules. But there are lots of unanswered questions about how it interacts with HD lookahead and so on. --f46d043bdf5ea0ef9f050f8896f4 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Ah, I see, I didn't catch that this scheme relies on UTXO commitments = (presumably with Mark's PATRICIA tree system?).

If you're doing a binary search over block contents then does that im= ply multiple protocol round trips per synced block? I'm still having tr= ouble visualising how this works. Perhaps you could write down an example r= un for me.

How does it interact with the need = to download chains rather than individual transactions, and do so without r= ound-tripping to the remote node for each block? Bloom filtering currently = pulls down blocks in batches without much client/server interaction and tha= t is useful for performance.

Like I said, I'd = rather just junk the whole notion of chain scanning and get to a point wher= e clients are only syncing headers. If nodes were calculating a script->= (outpoint, merkle branch) map in LevelDB and allowing range queries over it= , then you could quickly pull down relevant UTXOs along with the paths that= indicated they did at one point exist. Nodes can still withhold evidence t= hat those outputs were spent, but the same is true today and in practice th= is doesn't seem to be an issue.

The primary ad= vantage of that approach is it does not require a change to the consensus r= ules. But there are lots of unanswered questions about how it interacts wit= h HD lookahead and so on.

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