Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 8A234CB9 for ; Mon, 30 Oct 2017 22:14:48 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from mail.bluematt.me (mail.bluematt.me [192.241.179.72]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 378D5483 for ; Mon, 30 Oct 2017 22:14:47 +0000 (UTC) Received: from [172.17.0.2] (gw.vpn.bluematt.me [144.217.106.88]) by mail.bluematt.me (Postfix) with ESMTPSA id F303118119B; Mon, 30 Oct 2017 22:14:45 +0000 (UTC) To: Mark Friedenbach , Bitcoin Protocol Discussion References: <64173F46-551E-4C36-A43A-5FBDBFF761CD@friedenbach.org> From: Matt Corallo Message-ID: <1689d7c6-7c32-aa78-6626-c344f19923de@mattcorallo.com> Date: Mon, 30 Oct 2017 18:14:44 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <64173F46-551E-4C36-A43A-5FBDBFF761CD@friedenbach.org> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=0.0 required=5.0 tests=none autolearn=disabled version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Subject: Re: [bitcoin-dev] Simplicity: An alternative to Script 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, 30 Oct 2017 22:14:48 -0000 Are you anticipating it will be reasonably possible to execute more complicated things in interpreted form even after "jets" are put in place? If not its just a soft-fork to add new script operations and going through the effort of making them compatible with existing code and using a full 32 byte hash to represent them seems wasteful - might as well just add a "SHA256 opcode". Either way it sounds like you're assuming a pretty aggressive soft-fork cadence? I'm not sure if that's so practical right now (or are you thinking it would be more practical if things were drop-in-formally-verified-equivalent-replacements?). Matt On 10/30/17 17:56, Mark Friedenbach wrote: > Script versions makes this no longer a hard-fork to do. The script > version would implicitly encode which jets are optimized, and what their > optimized cost is. > >> On Oct 30, 2017, at 2:42 PM, Matt Corallo via bitcoin-dev >> > > wrote: >> >> I admittedly haven't had a chance to read the paper in full details, >> but I was curious how you propose dealing with "jets" in something >> like Bitcoin. AFAIU, other similar systems are left doing hard-forks >> to reduce the sigops/weight/fee-cost of transactions every time they >> want to add useful optimized drop-ins. For obvious reasons, this seems >> rather impractical and a potentially critical barrier to adoption of >> such optimized drop-ins, which I imagine would be required to do any >> new cryptographic algorithms due to the significant fee cost of >> interpreting such things. >> >> Is there some insight I'm missing here? >> >> Matt >> >> On October 30, 2017 11:22:20 AM EDT, Russell O'Connor via bitcoin-dev >> > > wrote: >> >> I've been working on the design and implementation of an >> alternative to Bitcoin Script, which I call Simplicity.  Today, I >> am presenting my design at the PLAS 2017 Workshop >> on Programming Languages and >> Analysis for Security.  You find a copy of my Simplicity paper at >> https://blockstream.com/simplicity.pdf >> >> >> Simplicity is a low-level, typed, functional, native MAST language >> where programs are built from basic combinators.  Like Bitcoin >> Script, Simplicity is designed to operate at the consensus layer.  >> While one can write Simplicity by hand, it is expected to be the >> target of one, or multiple, front-end languages. >> >> Simplicity comes with formal denotational semantics (i.e. >> semantics of what programs compute) and formal operational >> semantics (i.e. semantics of how programs compute). These are both >> formalized in the Coq proof assistant and proven equivalent. >> >> Formal denotational semantics are of limited value unless one can >> use them in practice to reason about programs. I've used >> Simplicity's formal semantics to prove correct an implementation >> of the SHA-256 compression function written in Simplicity.  I have >> also implemented a variant of ECDSA signature verification in >> Simplicity, and plan to formally validate its correctness along >> with the associated elliptic curve operations. >> >> Simplicity comes with easy to compute static analyses that can >> compute bounds on the space and time resources needed for >> evaluation.  This is important for both node operators, so that >> the costs are knows before evaluation, and for designing >> Simplicity programs, so that smart-contract participants can know >> the costs of their contract before committing to it. >> >> As a native MAST language, unused branches of Simplicity programs >> are pruned at redemption time.  This enhances privacy, reduces the >> block weight used, and can reduce space and time resource costs >> needed for evaluation. >> >> To make Simplicity practical, jets replace common Simplicity >> expressions (identified by their MAST root) and directly implement >> them with C code.  I anticipate developing a broad set of useful >> jets covering arithmetic operations, elliptic curve operations, >> and cryptographic operations including hashing and digital >> signature validation. >> >> The paper I am presenting at PLAS describes only the foundation of >> the Simplicity language.  The final design includes extensions not >> covered in the paper, including >> >> - full convent support, allowing access to all transaction data. >> - support for signature aggregation. >> - support for delegation. >> >> Simplicity is still in a research and development phase.  I'm >> working to produce a bare-bones SDK that will include >> >> - the formal semantics and correctness proofs in Coq >> - a Haskell implementation for constructing Simplicity programs >> - and a C interpreter for Simplicity. >> >> After an SDK is complete the next step will be making Simplicity >> available in the Elements project >> so that anyone can start experimenting with Simplicity in >> sidechains. Only after extensive vetting would it be suitable to >> consider Simplicity for inclusion in Bitcoin. >> >> Simplicity has a long ways to go still, and this work is not >> intended to delay consideration of the various Merkelized Script >> proposals that are currently ongoing. >> >> _______________________________________________ >> bitcoin-dev mailing list >> bitcoin-dev@lists.linuxfoundation.org >> >> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >