From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 08A90C016F for ; Wed, 10 Jun 2020 06:47:41 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id EC391869E1 for ; Wed, 10 Jun 2020 06:47:40 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id uy-YSoPfmHb9 for ; Wed, 10 Jun 2020 06:47:39 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail-40141.protonmail.ch (mail-40141.protonmail.ch [185.70.40.141]) by fraxinus.osuosl.org (Postfix) with ESMTPS id 59A0386920 for ; Wed, 10 Jun 2020 06:47:39 +0000 (UTC) Date: Wed, 10 Jun 2020 06:47:28 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com; s=protonmail; t=1591771657; bh=0Nwu0L3BJXGlg6zMZv5UvAdaWWiAU6E41fYw3rP+k7U=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=UHoAJ8eLDGEoPybPqzhwrTsNQ3CQS6f88ufAr/gVjV9LPfrYpkj1Mc+HRRw4coRnl UmK2Di91JPUG8+Odw00BMpcCMo5IliPNnQPV9ti2vcenpzOboG2Lb3QV/KV2Mgaz9+ jomgdZPn5fCHEIU6/qkO2LnF33ZFVnULm87NMs/g= To: ZmnSCPxj , Bitcoin Protocol Discussion From: ZmnSCPxj Reply-To: ZmnSCPxj Message-ID: In-Reply-To: References: <7c0dc46538f96032596163c4a9f03dc2.squirrel@giyzk7o6dcunb2ry.onion> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [bitcoin-dev] Question about PayJoin effectiveness X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 10 Jun 2020 06:47:41 -0000 Good morning again Mr. Lee, > > I am trying to learn about payjoin. I have a couple concerns on its > > effectiveness. Are my concerns valid or am I missing something? > > concern 1 > > If it is known to be a payjoin transaction anyone could determine the > > sender the recipient and amount right? > > Lets assume that everyone has a single utxo because payjoin becomes com= mon > > use and payjoin consolidates utxos through "snowballing". If Alice has = a > > UTXO of 0.05 btc and Bob has a UTXO of 1.15 btc. Bob can be assumed to > > have more balance because he is a merchant and his customers payjoin hi= m > > payments alot. It is also helpful to remember that Bob cannot exist in isolation, and ther= efore, Bob probably has: * Employees. * Suppliers. * Shareholders. For example, suppose Bob holds in reserve a 0.05 BTC UTXO in a holding wall= et. Then Bob takes the 1.16 UTXO it got from Alice and transfers 1.12 BTC to th= e holding wallet: Bob merchant wallet 1.16 --___-- 1.17 Bob holding wallet Bob holding wallet 0.05 -- -- 0.04 Bob merchant wallet The above looks exactly like one of the "customer pays Bob" transactions, b= ut is in fact different. Then Bob uses the holding wallet to pay out to employees, suppliers, and sh= areholders, such as in a single large batched transaction, and then leaves = behind another 0.05 BTC in the holding wallet (or some random small number = of BTC) for the next time Bob has to pay to employees/suppliers/shareholder= s. So the transaction below: 1.16 --___-- 1.17 0.05 -- -- 0.04 *could* be interpreted as the 0.05 owner paying to the 1.16 owner, but in f= act that is just Bob preparing the incoming funds from the merchant front-e= nd for processing to send to its own liabilities. Regards, ZmnSCPxj