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 30956DD9 for ; Fri, 26 Feb 2016 21:42:28 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-ig0-f175.google.com (mail-ig0-f175.google.com [209.85.213.175]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id E7A31EE for ; Fri, 26 Feb 2016 21:42:26 +0000 (UTC) Received: by mail-ig0-f175.google.com with SMTP id y8so44459626igp.1 for ; Fri, 26 Feb 2016 13:42:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:date:message-id:subject:from:to :content-transfer-encoding; bh=qJQBsMusT4MIVYrh4oRBcQUOjNy7vYnnEmeZJ4rQ3Yw=; b=ckRZ6pEcDyal8ibawKmGaow7AAUJriRB8wCuaxnMjuyL+Pa2OlyA9XHuqhBvKwRreF TL/M/ZZ8vpUQnKnwgDXHAKlHwsnGlbopC7fBcyrIfgIDNdGJ3AV6eajB6Y9RMaxtfTr9 shdhD6PiifRg00POmVlqeHJb7IiFjkZdLkZJrJlylm+rgklBc7nobJSoE2eFb7Bd1KUg AgvF/g9Xh8vXqwM2T0YlLCI0nRsiyGP5gzZJq9yYGvVA8H6onGYFvTDxPteNRkc5Foes jk/68lywwYiGF/fpePnCZQaZGp0FXpt5TY+10pUKGle68e8sE1NjGBC0kqL6OH0lVKKb +ekA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:date:message-id:subject:from :to:content-transfer-encoding; bh=qJQBsMusT4MIVYrh4oRBcQUOjNy7vYnnEmeZJ4rQ3Yw=; b=f7q2cMjtQiph9WAOZh0KRL2Pk8de8OlPCMXyizj4iMrEiuxLTDY2NPHpuoEVfzoL7k NCl1FHwqTGjjL4chux89R4ViSLwciHa5oVI5K66iGIKZbFoOdUGVUIDJ2Zh7qv1EkSRl W+SnPFIe+v8jwTY85huYjv4yYzwvr83Zg+mUQ1OTidcINq89tDJ1uPhYnXc5m9dPc5ry M1+49npPmZ5O3LZqGBJfEuqcF1CtNZ7mBZsFLOFoCb7AsKxp/OGt6kzkBYnMWzNr5vof dLamlJ8zm2Tx3NcoLADqdkzs6wzzeGQg5cX7ajvxeYG1jRjYo0cw86I5XAqEtlXRCNDL SSKw== X-Gm-Message-State: AD7BkJLoKfEG8HVvPPJM9wJp9cBM6JZcafjRSLoDOdLSRCigxbNo12pqKsvlcyewutu8/9MKUnp8GFBof6akTw== MIME-Version: 1.0 X-Received: by 10.50.41.102 with SMTP id e6mr133168igl.62.1456522946346; Fri, 26 Feb 2016 13:42:26 -0800 (PST) Sender: gmaxwell@gmail.com Received: by 10.107.132.75 with HTTP; Fri, 26 Feb 2016 13:42:26 -0800 (PST) Date: Fri, 26 Feb 2016 21:42:26 +0000 X-Google-Sender-Auth: HeJtCXN23LYavGVywTkZ0AJaaWg Message-ID: From: Gregory Maxwell To: Bitcoin Dev Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, FREEMAIL_FROM, 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 Subject: [bitcoin-dev] The first successful Zero-Knowledge Contingent Payment X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Development Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 26 Feb 2016 21:42:28 -0000 I am happy to announce the first successful Zero-Knowledge Contingent Payment (ZKCP) on the Bitcoin network. ZKCP is a transaction protocol that allows a buyer to purchase information from a seller using Bitcoin in a manner which is private, scalable, secure, and which doesn=E2=80=99t require trusting anyone: the expected information is transferred if and only if the payment is made. The buyer and seller do not need to trust each other or depend on arbitration by a third party. Imagine a movie-style =E2=80=9Cbriefcase swap=E2=80=9D (one party with a br= iefcase full of cash, another containing secret documents), but without the potential scenario of one of the cases being filled with shredded newspaper and the resulting exciting chase scene. An example application would be the owners of a particular make of e-book reader cooperating to purchase the DRM master keys from a failing manufacturer, so that they could load their own documents on their readers after the vendor=E2=80=99s servers go offline. This type of s= ale is inherently irreversible, potentially crosses multiple jurisdictions, and involves parties whose financial stability is uncertain=E2=80=93meaning that both parties either take a great deal of ris= k or have to make difficult arrangement. Using a ZKCP avoids the significant transactional costs involved in a sale which can otherwise easily go wrong. In today=E2=80=99s transaction I purchased a solution to a 16x16 Sudoku puz= zle for 0.10 BTC from Sean Bowe, a member of the Zcash team, as part of a demonstration performed live at Financial Cryptography 2016 in Barbados. I played my part in the transaction remotely from California. The transfer involved two transactions: 8e5df5f792ac4e98cca87f10aba7947337684a5a0a7333ab897fb9c9d616ba9e 200554139d1e3fe6e499f6ffb0b6e01e706eb8c897293a7f6a26d25e39623fae Almost all of the engineering work behind this ZKCP implementation was done by Sean Bowe, with support from Pieter Wuille, myself, and Madars Virza. Read more, including technical details at https://bitcoincore.org/en/2016/02/26/zero-knowledge-contingent-payments-an= nouncement/ [I hope to have a ZKCP sudoku buying faucet up shortly. :) ]