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 DA78E10A5 for ; Tue, 15 Oct 2019 18:31:36 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-wr1-f53.google.com (mail-wr1-f53.google.com [209.85.221.53]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 596736CE for ; Tue, 15 Oct 2019 18:31:36 +0000 (UTC) Received: by mail-wr1-f53.google.com with SMTP id n14so25026284wrw.9 for ; Tue, 15 Oct 2019 11:31:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=eZJYiTrZh0tc69YyXXwnStRl0FoS8EL5pk8ZCEgn5GY=; b=L/38gdeeRy1faaxp7jUOIpnoodU8Cvv1F6wvdq31j16WFSo9H5ghR8uwaA+Vqo/Xrr 51vR9+z1YAjUeq0Ej6E3pGk7TXl6+SPDnU7qj9JNdeWEO8H5qP8Gmr2SsWaMaUm1v3rz rISUV+Zn34JxFm32uo5BsEMIb8GadTzo/LEdeC4MOFbvuYda5mRXFmzRbVnHNNopi6ox W2df3hbjjJnShWkA/Lr87a49VWCljKbwqWE1P38VlU6QoY4krTpowRRuJke2ahLDe8YT VoD+W3dSkswy9ZIRsREVBaIbBeCOOJqtpSbQd/vnlBlyd+UfA171sxW4OKY0iLptWhZZ cZzw== 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=eZJYiTrZh0tc69YyXXwnStRl0FoS8EL5pk8ZCEgn5GY=; b=A5GSnXetAIztKd1TLSI5ceiPHur1XIL5aJMJ97IY9/Fs2i7dD5BXGloZRjdtGM0hTt luGXXZ8nyCoBbRMm6JX+zefmCTTn8dTx4bzuuLNrrWet3aOCZEYZPwd6+v5mG5wOCnWi hEnW1hsi/4E23GlXDXYbHYgTw2hylTL1hJPu6zIwtod2cKJMuHD6lFdtWOBv3eR7cwQm b5OXhFjNFK9+XF3pUui364Z4pr37HXVQjm6cu1bTHYGB+hsZ5Wc91DAF6E3oVVHBgNum 5BeTSPmsiN7J8/PHm7Jq7DiM5czrwqx4cidhDcPMhM7lIQyXYoKVWlbVsPU9INZHdyyD Y+Vw== X-Gm-Message-State: APjAAAWeiIlg9yCRnD6yBwhIGsROKMqz6sErVR3Ra8R+Lw/FJ3YNgdRH lfvkghXhWuAL3c+hvRnIf7nNm4X524fcKHTXVP9Yww== X-Google-Smtp-Source: APXvYqztidOzEhNOe5PXrskwXsGBefR/RH4X0dTxriESUfYnAyMjVZWr87+757YXFwAzXhWz/dDx4gxvSOO/+OEnEoI= X-Received: by 2002:adf:fc42:: with SMTP id e2mr8266570wrs.100.1571164294809; Tue, 15 Oct 2019 11:31:34 -0700 (PDT) MIME-Version: 1.0 References: <42cd5ffd-63e8-b738-c4ea-13d0699b1268@purse.io> <93649df9-27ab-abaf-00f3-da6c528344cc@purse.io> In-Reply-To: <93649df9-27ab-abaf-00f3-da6c528344cc@purse.io> From: Tier Nolan Date: Tue, 15 Oct 2019 19:30:58 +0100 Message-ID: To: Braydon Fuller via bitcoin-dev Content-Type: multipart/alternative; boundary="000000000000ad0d030594f7316c" 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 Subject: Re: [bitcoin-dev] Chain width expansion 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, 15 Oct 2019 18:31:37 -0000 --000000000000ad0d030594f7316c Content-Type: text/plain; charset="UTF-8" On Tue, Oct 15, 2019 at 7:29 AM Braydon Fuller via bitcoin-dev < bitcoin-dev@lists.linuxfoundation.org> wrote: > So I don't think you can use the height in the coinbase for that > purpose, as it's not possible to validate it without the previous > headers. That's common for more than just the height. > It is a property of blockchains that the lowest digest for a chain represents the total chainwork. Estimate total hash count = N * (2^256) / (Nth lowest (i.e. strongest) digest over all headers) To produce a fake set of 10 headers that give a higher work estimate than the main chain would require around the same effort as went into the main chain in the first place. You might as well completely build an alternative chain. Working backwards for one of those headers, you have to follow the actual chain back to genesis. --000000000000ad0d030594f7316c Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Tue, Oct 15, 2019 at 7:29 AM Braydon Fuller via bitcoin-dev <<= a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.l= inuxfoundation.org> wrote:
So I don't think you can use the height in the coinbase for that
purpose, as it's not possible to validate it without the previous
headers. That's common for more than just the height.
<= div>
It is a property of blockchains that the lowest digest f= or a chain represents the total chainwork.

Estimat= e total hash count =3D N * (2^256) / (Nth lowest (i.e. strongest) digest ov= er all headers)

To produce a fake set of 10 he= aders that give a higher work estimate than the main chain would require ar= ound the same effort as went into the main chain in the first place.=C2=A0 = You might as well completely build an alternative chain.

=
Working backwards for one of those headers, you have to follow t= he actual chain back to genesis.
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