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 97181B7A for ; Thu, 19 Sep 2019 15:47:25 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-ot1-f48.google.com (mail-ot1-f48.google.com [209.85.210.48]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 27C6F711 for ; Thu, 19 Sep 2019 15:47:25 +0000 (UTC) Received: by mail-ot1-f48.google.com with SMTP id b2so3483996otq.10 for ; Thu, 19 Sep 2019 08:47:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=8uIu5CvSESqImzKSwTa91vQf+QhlO3JkjKQXyG2EWY4=; b=jnZWMa1+9OjZIZLrxvnr/l8Z/YVRvfjyJwI1pdbK0B/kAaFRCSK2mvhAk2GWdDh8+m FItuZtcWDLovcNmZJzw2uTpiLuEkQxHvbGhGJLeuWfA2++ZNT7xIYoJ59D60BdYPhizm YkvaYPtM+wK8TpdSVcRQUGkf7Zea2UzFNkkUaISUGsKF30qv2kzK6q9Xbnf9hDESicD6 A9G+ExWu4sWjnbbUpCtrLLk3oa0jxR572TYT1sTMhPjWfa0LzHgtyW9oUPL+x1i7m9vf BpSK8sQo8OxcMPcnwUy2TEdVNOD/7KciEvrdEXqeUhvrRgR+hBejgDBsaChCR7DbKsAj eO3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=8uIu5CvSESqImzKSwTa91vQf+QhlO3JkjKQXyG2EWY4=; b=nKhqnP4OGl2/a86+JmsLd5pMmJcQMW3/ImK9/dAC8TiCGCgQTUWkUCbAdwiG4hpQEA NPMyFdgkJtRrLLsnvn29DCeoNjTMIVS272U/xGk/tqk97HHBhUC7wjKj8b6nNN8g/hMv VoxDEWZFWR8hH4cW0HX6+xFV05+CU8HCALl5H2LnqFwk63VE/G8Dc5O3ZlIPzdFyJxD+ 5u4AwFWSzmKZjG1U+LlZMBgyXdUG8zZHUHOCWLrdn8sA+vOpuiOeMypg3Okaci03yQbZ bJFQTUA9fGg3fTammf+5LXmOBJk5+zh71NhEBHcec/qkYiKGMnj/haCZjNey2+lrAzWf QeBA== X-Gm-Message-State: APjAAAWV+I/4hiPMd+/UX7bT4/R+PBQPseLZIO+nqvBgUwqmp79GNG1p dP5MCH9KhtQkRE2x6B4zbXCd9MkBsmydczAHhg== X-Google-Smtp-Source: APXvYqzhILnRXkLMbIm1OYgnt2IRHXRcj6T7JgRh7RHCbyGfK4moSTdBD38H0VzjjWMxxVd5I1pSTlC2khk8aDo6UoU= X-Received: by 2002:a9d:7d17:: with SMTP id v23mr1743857otn.81.1568908044353; Thu, 19 Sep 2019 08:47:24 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: John Tromp Date: Thu, 19 Sep 2019 17:47:12 +0200 Message-ID: To: ZmnSCPxj Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, 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: Thu, 19 Sep 2019 15:52:54 +0000 Cc: Bitcoin Protocol Discussion Subject: Re: [bitcoin-dev] Timelocks and Lightning on MimbleWimble 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: Thu, 19 Sep 2019 15:47:25 -0000 dear ZmnSCPxj, > Which I suppose is my point: you lose some of the "magic shrinking blockc= hain" property in implementing relative locktimes, as you now increase the = data you have to store forever (i.e. the kernels). The "magic shrinking" of MW never applied to kernels. To validate the current UTXO set, you need to validate *all* the kernels, each of which is a Pedersen commitment to zero together with a Schnorr signature using said commitment as public key. Then you need to check that the sum of UTXO commitments (outputs) minus the summed block rewards times G (inputs) equals the sum of kernel commitments. Basically, the same check that is applied to individual transactions. > It seems to me that Poon-Dryja and Decker-Wattenhofer can be "directly" p= orted over to any MimbleWimble blockchain with relative locktimes. > Reference [5] seems to be Poon-Dryja ported over to using relative lockti= mes for MimbleWimble. Yes, Beam's design is a straightforward port of Poon-Dryja. > Decker-Russell-Osuntokun ("eltoo") is harder due to the `SIGHASH_NOINPUT`= requirement. > I have tried to derive an equivalent to this `SIGHASH_NOINPUT` somehow by= considering that the "reference to previous kernel" as being akin to the B= itcoin transaction input referring to a previous output, however it seems t= o be not easy to create a retargatable "reference to previous kernel" in th= is way. The Grin "Elder channel" design of [3] is similar in spirit to eltoo though, as the revocation transaction can be combined with the final close transaction to counter any closing attempt to an obsolete state. The design also offers some bandwidth savings compared to the Poon-Dryja design. > In any case, it seems to me that the loss of SCRIPT does not prevent a Mi= mbleWimble blockchain from using an offchain updateable cryptocurrency syst= em. Correct; lack of scripts is not as much of a handicap for MW as it appears. Multi-sig, atomic swaps, and payment channels are all possible. regards, -John