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 C2D56491 for ; Mon, 11 Mar 2019 16:36:39 +0000 (UTC) X-Greylist: delayed 00:35:19 by SQLgrey-1.7.6 Received: from pectw.vm.bytemark.co.uk (pectw.vm.bytemark.co.uk [80.68.92.123]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 79C7E2C4 for ; Mon, 11 Mar 2019 16:36:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=pectw.net; s=dkim_test; h=Content-Type:Content-Transfer-Encoding:MIME-Version: Message-ID:Date:Subject:To:From:Sender:Reply-To:Cc:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=TfJ/frtl4yxyc3iw4jAjxJXyYB/jn3my/9HEL0LatKI=; b=EU9UEtrsFknYx9wHS3xcuMVyjR lx7255AlLNdmfgTgCTRWsdAQuEkq+vxcG/uI4DDEEIMig7oRoF8hZ3za2Q9HGfr3ATzoEUthKIypQ HkR456egkkNTEiapaJHs56lkU; Received: from host81-140-222-88.range81-140.btcentralplus.com ([81.140.222.88] helo=svetlana.localhost) by pectw.vm.bytemark.co.uk with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1h3NMX-0007Wh-F0 for bitcoin-dev@lists.linuxfoundation.org; Mon, 11 Mar 2019 16:01:13 +0000 From: Alistair Mann To: bitcoin-dev@lists.linuxfoundation.org Date: Mon, 11 Mar 2019 16:01:12 +0000 Message-ID: <12139028.TiJ4v5RR02@dprfs-d5766> User-Agent: KMail/4.14.2 (Linux/4.4.0-18-generic; KDE/4.14.2; x86_64; ; ) MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU 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: Mon, 11 Mar 2019 16:43:46 +0000 Subject: [bitcoin-dev] Pre BIP: Solving for spam and other abuse with an HTLB 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: Mon, 11 Mar 2019 16:36:39 -0000 Greetings all, I'm looking for thoughts on the BIPability of a relatively minor change, with an outsize benefit, with the provisional name 'Hashed Time-Locked Bond', HTLB for short. The minor change is to implement HTLC without its digest element. The outsize benefit is to incentivise against spam and other abuse. In this post I'll introduce the script, motivation, a working proof-of-concept site, and then round out addressing the desirability of a BIP. Implementation of HTLB: The script takes the form: OP_IF OP_DUP OP_HASH160 OP_ELSE [TIMEOUTOP] OP_DROP OP_DUP OP_HASH160 OP_ENDIF OP_EQUALVERIFY OP_CHECKSIG Notice that this is the script of BIP-0199 with '[HASHOP] OP_EQUALVERIFY' removed. A worked example. Alice is the buyer and Bob the seller. Alice knows that Bob is her father and that he doesn't know her new email address. She commits 50,000 satoshis to the above script with a 24 hour timeout, then sends proof of that transaction along with an email reintroducing herself. Bob's MUA recognises that the bond is good and alerts him to the email from a strange sender: he knows that if he disagrees with the implicit assertion that he will want that email, he has 24 hours to redeem those funds at the sender's expense. He reads the email. Bob is incentivised not to redeem against his daughter though, and lets the timeout expire: Alice reclaims her funds. Carol did not bond at all, so her email was refused at the server. Dave's bond of 100 satoshis was too small to pass Bob's minimum, so his email too was refused at the server. Erin guaranteed 50,000 satoshis each to reach Bob and ten thousand others with an email offering triple-glazed windows: she's now well on the way to losing them all. Motivation: There is a transaction class we can identify as 'Good Behaviour Bonds' currently poorly served in Bitcoin*. Bail bonds and bar tabs are real world exemplars. Conceptually, Alice guarantees Bob she will do or be something for a fixed period: if she complies Bob refrains from redeeming her guarantee; if she does not comply Bob redeems some or all of it. It's inherent to the class that Alice is incentivised within the transaction to good behaviour outside it. Conversely, Bob is incentivised outside the transaction to good behaviour within it. In essence, Alice commits funds to a penalty in advance of a connection to Bob. Alice is incentivised by getting her funds back, Bob is incentivised by her - and others - continued patronage. This transaction class can protect any addressable resource. Alice can therefore guarantee Bob that: 1. Her email to him is not spam 2. Her telephone call to him is not a robocall 3. Her posts to his website are not flamebait. In each case this is handled by extending the protocol concerned to detect for and change behaviour depending on Alice's proof of bond. That Alice can guarantee her behaviour to addressable resources means she can also guarantee her behaviour to non-addressable resources. She could guarantee: 1. a group chat that she won't upload NSFW content 2. an IRC channel that she won't flood 3. a streamed multiplayer game that she won't swear over teamspeak. This is accomplished by use of an addressable resource and an enforcement mechanism such as IRC's devoice command. Alice can also guarantee her behaviour offline in much the same way. She can guarantee to: 1. a magistrate that she'll appear for trial by a given date (Bail bond/ Surety) 2. a houseowner that she'll cover costs incurred from cleaning up after her (Rental/Security deposit) 3. an innkeeper that she can pay for the drinks she's ordering (Bar tab) That a transaction has been entered into online can be proved offline, so these can be accomplished by means of an online, addressable resource and an offline plaintext token. Live site: I have put up a live proof-of-concept at http://berewic.com. This protects a specific URL accessed through HTTP (the "demo page") whereby visitors who have posted bond on testnet3 get different content than those who have not posted bond, or whose bond has expired. This is accomplished through an experimental protocol where an agent with a hot wallet speaks for a credentialed user in a similar way to how SMTP speaks for an email's original sender. That protocol would seem to be outside the scope of the proposed BIP but I'm happy to elaborate if required. A short video demonstrating live use of the HTLB is also posted there. BIP: Name: "Hashed Time-Locked Bond" seems a reasonable name - the script is still hashed even if the digest is gone, and HTLB nicely scans like HTLC - 1. It won't have escaped notice that the HTLB script can be wholly written in an HTLC script: 'HTLB over HTLC', however there are additional reasons to consider HTLB for a separate BIP: 1. Alternative implementations using HTLB over HTLC would need to standardise on what the redundant [HASHOP] and should be 2. Using HTLB over HTLC is inefficient as it compels unused storage and unnecessary processing 3. Amending or superceding BIP-0199 to recognise the digest element as optional creates backward compatibility issues 4. Recognising the motivation onchain would help inform second-layer solutions where HTLB would be even more useful (eg, I believe that HTLCs and HTLBs do not have analogues in the Lightning Network) 5. Wallet support. A limiting factor for the live site above has been the lack of wallet HTLC support to the point that the demo does not implement CHECKSIG. HTLC & HTLB signing would ideally take place in the wallet that must be present, and so a BIP would help bolster the case for, and inform anyone revisiting, PR7601. Thoughts? * The HTLB lives in the space somewhere near https://en.bitcoin.it/wiki/Fidelity_bonds and https://en.bitcoin.it/wiki/Contract#Example_1:_Providing_a_deposit. The former requires an unnecessary sacrifice, the latter does not allow for penalisation.