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 3D15F483 for ; Sun, 18 Sep 2016 16:05:30 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from outmail148102.authsmtp.net (outmail148102.authsmtp.net [62.13.148.102]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 71621144 for ; Sun, 18 Sep 2016 16:05:29 +0000 (UTC) Received: from mail-c247.authsmtp.com (mail-c247.authsmtp.com [62.13.128.247]) by punt20.authsmtp.com (8.14.2/8.14.2/) with ESMTP id u8IG5RFB054432; Sun, 18 Sep 2016 17:05:27 +0100 (BST) Received: from petertodd.org (ec2-52-5-185-120.compute-1.amazonaws.com [52.5.185.120]) (authenticated bits=0) by mail.authsmtp.com (8.14.2/8.14.2/) with ESMTP id u8IG5PnI064503 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sun, 18 Sep 2016 17:05:26 +0100 (BST) Received: from [127.0.0.1] (localhost [127.0.0.1]) by petertodd.org (Postfix) with ESMTPSA id 73AB740120; Sun, 18 Sep 2016 16:01:45 +0000 (UTC) Received: by localhost (Postfix, from userid 1000) id A315920850; Sun, 18 Sep 2016 12:05:24 -0400 (EDT) Date: Sun, 18 Sep 2016 12:05:24 -0400 From: Peter Todd To: Jannes Faber Message-ID: <20160918160524.GA13307@fedora-21-dvm> References: <20160918042001.GA9076@fedora-21-dvm> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="fdj2RfSjLxBAspz7" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-Server-Quench: b6bcfc4f-7db9-11e6-bcde-0015176ca198 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCd2Yg0TA1ZNQRgX IjsJECJaVQIpKltL GxAVKBZePFsRUQkR aAdMdwoUC1AEAgsB AmAbWlNeUFh7W2U7 bghPaBtcak9QXgdq T0pMXVMcUQ0Rdhlh WGceVB13dwYIcH13 YQgwWCIIChd+I1t6 FhxdCGwHMGF9OjNL BV1YdwJRcQRMLU5E Y1gxNiYHcQ5VPz4z GA41ejw8IwAXCSJJ TxsVN18OQEAEVjgA RhUPVTsoBwUZRyh7 NwE8MlkHEQ4WPCd6 G1o9UlUZNVobFhFT BF1ADGdFJlwMXDYi CBtBNQAA X-Authentic-SMTP: 61633532353630.1038:706 X-AuthFastPath: 0 (Was 255) X-AuthSMTP-Origin: 52.5.185.120/25 X-AuthVirus-Status: No virus detected - but ensure you scan with your own anti-virus system. X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Cc: Bitcoin Dev Subject: Re: [bitcoin-dev] Interpreting nTime for the purpose of Bitcoin-attested timestamps 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: Sun, 18 Sep 2016 16:05:30 -0000 --fdj2RfSjLxBAspz7 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Sep 18, 2016 at 03:45:40PM +0200, Jannes Faber wrote: > Would you not also have to consider (all) earlier blocks? >=20 > T =3D max(block[i].nTime for i in {x-100, ..., x, ..., x + N-1}) + max_of= fset >=20 > In case one or more previous blocks have an nTime considerably in the > future and blocks>=3D x have honest nTimes (or before true time). >=20 > Maybe not strictly for the goal you were describing here (conservative > estimate) but rather to prevent distinct timestamp events seeming to have > happened in the wrong order? Well that's the thing: timestamps are simply proofs that something existed prior to some time, nothing more, nothing less. So it doesn't make sense for there to be any notion of the "wrong order" in= a timestamp proof; the proof either is or is not valid, but that has nothing = to do with other proofs. Additionally, the architecture of OpenTimestamps does= n't and can't make any 100% guarantees about the apparent order of timestamps, because it's always possible for an earlier timestamp to end up committed in the blockchain after a later timestamp gets committed. It's not all that li= kely of an event, but it is possible. If you don't want that to be possible, you're going to need a dedicated cha= in of transactions for your particular purpose, which adds a lot of complexity, cost, and makes it much harder to achieve the same level of availability for the service as a whole. Remember that for many use-cases the user experience is that there's two or more claimed dates, and OpenTimestamps simply verifies that those dates are plausible. Take for example, timestamped git commits: commit 536411e73b8c23dc2fdfd78052c893f578444926 ots: Got 2 attestation(s) from cache ots: Success! Bitcoin attests data existed as of Thu Sep 15 01:07:08 20= 16 EDT ots: Good timestamp gpg: Signature made Thu 15 Sep 2016 12:10:25 AM EDT gpg: using RSA key 6399011044E8AFB2 gpg: Good signature from "Peter Todd " gpg: aka "[jpeg image of size 5220]" Author: Peter Todd Date: Thu Sep 15 00:10:20 2016 -0400 Release v0.2.0 Here we have the date on the git commit, another date a few seconds later f= or the PGP signature, and a third date an hour later for the Bitcoin timestamp, attesting to the fact that the two other dates for that one git commit are plausible. --=20 https://petertodd.org 'peter'[:-1]@petertodd.org --fdj2RfSjLxBAspz7 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- iQEcBAEBCAAGBQJX3rtBAAoJEGOZARBE6K+yH5UH/2aeDx8Rdm5ayeiLStwmPlOZ KrL/0mWocusEiSZWyOrqSUPVsKXGsAbd+q0nja43SVNbsBmijwlyUHvS20RCHDVm vlrH5D1ibE8pfwaUMzTsh02bWsaNDbU5l2BsuG29fJE8HanGwnvE5JYE4PT+9PHh 2uQfQcsvrtjnfNH9xBuAnK3S/9hTZU6ZZuP10h8o0ANSzcrAMvGBe0qUEQv/USok /mWIzIoZEvshjC0zHWGUhk4sJn+R2kgf3BAbxjLOWPPO5vPko2qNBE9vGAFI92Ai BBohfbOijUbmefing+KgahDOdnbWWFxRllv375HGrIdbryUEtaUHOJPIQ+mEpRM= =3EF+ -----END PGP SIGNATURE----- --fdj2RfSjLxBAspz7--