Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id CD67349F for ; Sat, 22 Dec 2018 16:56:43 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from sender-of-o51.zoho.com (sender-of-o51.zoho.com [135.84.80.216]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 3E9B5CF for ; Sat, 22 Dec 2018 16:56:42 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; t=1545497796; cv=none; d=zoho.com; s=zohoarc; b=cw5gQtlwjOnfbgZKtB7XH5jKJ0tyMqL0wmmZaomLLaEH4+m+J7khoClUsHrqb4QU2CNqx5xmqVP7aD6M65E2CnBGTaN7fCJqyVjQv+YwUnAXEeep77IKZkScNI08kTB+g10GI7Y6klPqq4EsJcA7tZafFmiIy14DyIukweCSrPw= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1545497796; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:To:ARC-Authentication-Results; bh=i4heNDv/Iof8aXNHOEx104O7ColF8uPlhq6cNq7ybIg=; b=grJ8X2LiLiOtZQY58cIFBhWSLlppEx7gp1LfXFrh17wPW3zIVGAhrFBfngoNYwRWEJom0Bmpn2m7c2a6V3LVVz94pC0VuqbCiTq8TSOq9hKKw1gI90K0VhjQhSNv8/n070hZtRok1leNkE3bUOVlYpEAqCRKN8hAphBNAjNNh3Q= ARC-Authentication-Results: i=1; mx.zoho.com; dkim=pass header.i=xbt.hk; spf=pass smtp.mailfrom=jl2012@xbt.hk; dmarc=pass header.from= header.from= Received: from [10.8.0.105] (n218103234118.netvigator.com [218.103.234.118]) by mx.zohomail.com with SMTPS id 1545497794572562.9421070731885; Sat, 22 Dec 2018 08:56:34 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 12.0 \(3445.100.39\)) From: Johnson Lau In-Reply-To: Date: Sun, 23 Dec 2018 00:56:29 +0800 Content-Transfer-Encoding: quoted-printable Message-Id: References: <9F8C0789-48E9-448A-A239-DB4AFB902A00@xbt.hk> <8z5NQkaOUo9z-wdBphQtZrxIf7OCtVQFvK3neMWvcRsngld5XJs-vt7CLuY46ZOp_pX8gEd92pMdkEkp8CUOMH9lUTw5ocWsbDPiaKdSa2I=@protonmail.com> <34B38940-524D-42B9-8A67-6A62DCE04665@xbt.hk> To: ZmnSCPxj X-Mailer: Apple Mail (2.3445.100.39) X-ZohoMailClient: External X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,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 X-Mailman-Approved-At: Sun, 23 Dec 2018 18:43:54 +0000 Cc: bitcoin-dev Subject: Re: [bitcoin-dev] Safer NOINPUT with output tagging 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: Sat, 22 Dec 2018 16:56:44 -0000 > On 22 Dec 2018, at 10:25 PM, ZmnSCPxj wrote: >=20 > Good morning Johnson, >=20 >> Generally speaking, I think walletless protocol is needed only when = you want to rely a third party to open a offchain smart contract. It = could be coinswap, eltoo, or anything similar. >=20 > I think a third party would be pointless in general, but then I am = strongly against custodiality. >=20 > The idea is that you have some kind of hardware wallet or similar = "somewhat cold" storage *that you control yourself*, and crate channels = for your hot offchain Lightning wallet, without adding more transactions = from your somewhat-cold storage to your hot offchain Lightning wallet on = the blockchain. >=20 > Then you could feed a set of addresses to the hot offchain wallet = (addresses your somewhat-cold storage controls) so that when channels = are closed, the funds go to your somwhat-cold storage. >=20 > I also doubt that any custodial service would want to mess around with = deducting funds from what the user input as the desired payment. I have = not seen a custodial service that does so (this is not a scientific = study; I rarely use custodial services); custodial services will deduct = more from your balance than what you send, but will not modify what you = send, and will prevent you from sending more than your balance minus the = fees they charge for sending onchain. >=20 > Even today, custodial services deducting from your sent value (rather = than the balance remaining after you send) would be problematic when = interacting with merchants (or their payment processors) accepting = onchain payments; the merchant would refuse to service a lower value = than what it charges and it may be very technically difficult to recover = such funds from the merchant. > I expect such a custodial service would quickly lose users, but the = world surprises me often. >=20 > Regards, > ZmnSCPxj If the users are expected to manually operate a hardware wallet to fund = the channel, they might do stupid things like using 2 wallets to make 2 = txs, thinking that they could combine the values this way; or = =E2=80=9Crefilling=E2=80=9D the offchain wallet with the address, as you = suggested. While I appreciate the goal to separate the coin-selecting = wallet with the offchain wallet, I am not sure if we should rely on = users to do critical steps like entering the right value or not reusing = the address. Especially, the setup address should be hidden from = user=E2=80=99s view, so only a very few =E2=80=9Cintelligent advanced = users" could try to refill the channel. If we don=E2=80=99t rely on the user as the bridge between the hardware = wallet and the offchain wallet, we need a communication protocol between = them. With such protocol, there is no need to spend the setup TXO with = NOINPUT.=