From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 3794DBC5 for ; Fri, 30 Mar 2018 08:06:46 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-io0-f177.google.com (mail-io0-f177.google.com [209.85.223.177]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 86F615F4 for ; Fri, 30 Mar 2018 08:06:45 +0000 (UTC) Received: by mail-io0-f177.google.com with SMTP id b20so10375982iof.5 for ; Fri, 30 Mar 2018 01:06:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=fZfnW+2HObHwVYtPkWki6fTNBbXEBNmg0IYRPJ2Fq9U=; b=K/5qbvPCvX6zyEwnjRxN35kf3Uw9odUjqJExKd5ob2LFbLdz+bvVRqz8gL+TvPBGn9 DRmT4Fo3sOJUqOWH/4vfo6ixzJdWLmrc191vcxOwILdscFaYJkju3qR9rzpGDrLWIekj 5fSLZPtH5Wke0Z+B6Kbj8U5PkuGv3bX6ywYOtEyBQVS86eTl0q84JUL+WMgYsy8YJQ4C cSmsjFzb7T9O9uAcGBxe9672zYbjrlMngHgMceNp5EHBvxnPe5XWuMknC8omMa33zkEn LVN2bGd6r+PJWNkg9qSmULccJhUS2aEXh5QLAyX73x+jnhXI8zDK5ntVUYDvwN9zWE4b C7Ig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=fZfnW+2HObHwVYtPkWki6fTNBbXEBNmg0IYRPJ2Fq9U=; b=Ar3YzCc4+4VqxrFRh8a+HbjkzPl6Bh0cSSibxeEATMLkVUhfHgTCG0Hivemv2D2v5N 3pVtqlocrGZOma95rJWX+TeRpAsXwQbzC1ttFRdLr3KR3xpRExE5oMlRPc/S58/pP/0P Pgb8BgGNMk4eRsaof2nn2ltrq+joqlUowI/IXYXFEprh+jJD4b/VF3HD1dDU2UwzgwRz BQOtSH/vxTkK/jU5FfTCAIDDZEtcluEB1gpTCNEYRZ2KH/XK4NEwp/5kbMlvaZwTnhx5 +qhOQ7502BLVq+iQzpkInxyenmcVQJc4b0P66L7ch3xmFS3/tWyZKNJkyaQHbk9F3FNe 7TZw== X-Gm-Message-State: AElRT7EJPcuBqrBkpsZ/V7oWvDFqM2WS7y6b8/qaT34YSUB5BpXGBpRs uxL2H/q9B19vQmU48ueRYHrHYuqohbR2TPk+e/8= X-Google-Smtp-Source: AG47ELsLktS/R/aU9LZXiONyWK9lTfejQx03AiiZw8Ft/a5zu713p9gBBSO/URA8gmqNTPGN/PB8e37ldB37Wg5vTWs= X-Received: by 10.107.11.204 with SMTP id 73mr55020905iol.25.1522397204750; Fri, 30 Mar 2018 01:06:44 -0700 (PDT) MIME-Version: 1.0 Received: by 10.2.46.32 with HTTP; Fri, 30 Mar 2018 01:06:24 -0700 (PDT) In-Reply-To: <20180330061418.GA6017@erisian.com.au> References: <20180330061418.GA6017@erisian.com.au> From: Riccardo Casatta Date: Fri, 30 Mar 2018 10:06:24 +0200 Message-ID: To: Anthony Towns Content-Type: multipart/alternative; boundary="001a113de7a498a89f05689cb8c5" X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, 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: Sun, 01 Apr 2018 14:27:14 +0000 Cc: Bitcoin Protocol Discussion Subject: Re: [bitcoin-dev] Optimized Header Sync 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, 30 Mar 2018 08:06:46 -0000 --001a113de7a498a89f05689cb8c5 Content-Type: text/plain; charset="UTF-8" Yes, I think the checkpoints and the compressed headers streams should be handled in chunks of 2016 headers and queried by chunk number instead of height, falling back to current method if the chunk is not full yet. This is cache friendly and allows to avoid bit 0 and bit 1 in the bitfield (because they are always 1 after the first header in the chunk of 2016). 2018-03-30 8:14 GMT+02:00 Anthony Towns : > On Thu, Mar 29, 2018 at 05:50:30PM -0700, Jim Posen via bitcoin-dev wrote: > > Taken a step further though, I'm really interested in treating the > checkpoints > > as commitments to chain work [...] > > In that case, shouldn't the checkpoints just be every 2016 blocks and > include the corresponding bits value for that set of blocks? > > That way every node commits to (approximately) how much work their entire > chain has by sending something like 10kB of data (currently), and you > could verify the deltas in each node's chain's target by downloading the > 2016 headers between those checkpoints (~80kB with the proposed compact > encoding?) and checking the timestamps and proof of work match both the > old target and the new target from adjacent checkpoints. > > (That probably still works fine even if there's a hardfork that allows > difficulty to adjust more frequently: a bits value at block n*2016 will > still enforce *some* lower limit on how much work blocks n*2016+{1..2016} > will have to contribute; so will still allow you to estimate how much work > will have been done, it may just be less precise than the estimate you > could > generate now) > > Cheers, > aj > > -- Riccardo Casatta - @RCasatta --001a113de7a498a89f05689cb8c5 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Yes, I think the checkpoints and the compressed heade= rs streams should be handled in chunks of 2016 headers and queried by chunk= number instead of height, falling back to current method if the chunk is n= ot full yet.

This is cache friendly and allows to avoid bit 0 and bit 1 in the bi= tfield (because they are always 1 after the first header in the chunk of 20= 16).

<= div class=3D"gmail_quote">2018-03-30 8:14 GMT+02:00 Anthony Towns <aj@eris= ian.com.au>:
On Thu, Mar 29, 2018 at 05:50:30PM -0700, Jim Posen via bitcoin-dev wrot= e:
> Taken a step further though, I'm really interested in treating the= checkpoints
> as commitments to chain work [...]

In that case, shouldn't the checkpoints just be every 2016 blocks and include the corresponding bits value for that set of blocks?

That way every node commits to (approximately) how much work their entire chain has by sending something like 10kB of data (currently), and you
could verify the deltas in each node's chain's target by downloadin= g the
2016 headers between those checkpoints (~80kB with the proposed compact
encoding?) and checking the timestamps and proof of work match both the
old target and the new target from adjacent checkpoints.

(That probably still works fine even if there's a hardfork that allows<= br> difficulty to adjust more frequently: a bits value at block n*2016 will
still enforce *some* lower limit on how much work blocks n*2016+{1..2016} will have to contribute; so will still allow you to estimate how much work<= br> will have been done, it may just be less precise than the estimate you coul= d
generate now)

Cheers,
aj




--
Ri= ccardo Casatta - @RCasatta
--001a113de7a498a89f05689cb8c5--