From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.osuosl.org (smtp1.osuosl.org [IPv6:2605:bc80:3010::138]) by lists.linuxfoundation.org (Postfix) with ESMTP id C9FC9C0032 for ; Thu, 26 Oct 2023 01:54:24 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id ACCC7822A6 for ; Thu, 26 Oct 2023 01:54:24 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 smtp1.osuosl.org ACCC7822A6 Authentication-Results: smtp1.osuosl.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20230601 header.b=C/54VBiM X-Virus-Scanned: amavisd-new at osuosl.org X-Spam-Flag: NO X-Spam-Score: -2.098 X-Spam-Level: X-Spam-Status: No, score=-2.098 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URI_DOTEDU=0.001] autolearn=ham autolearn_force=no Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id s43Y_QLRR1ZK for ; Thu, 26 Oct 2023 01:54:23 +0000 (UTC) Received: from mail-ed1-x52a.google.com (mail-ed1-x52a.google.com [IPv6:2a00:1450:4864:20::52a]) by smtp1.osuosl.org (Postfix) with ESMTPS id 41B85822A4 for ; Thu, 26 Oct 2023 01:54:23 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 smtp1.osuosl.org 41B85822A4 Received: by mail-ed1-x52a.google.com with SMTP id 4fb4d7f45d1cf-53dd752685fso482380a12.3 for ; Wed, 25 Oct 2023 18:54:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1698285261; x=1698890061; darn=lists.linuxfoundation.org; h=content-transfer-encoding:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=IxyXRqXBDWI0lHk+KDRt8c4479uaLzWOf2qdkuFKABY=; b=C/54VBiM/uLPxZPcBemk3fHu/jdn+uHOZxoP4oqXNw5NESlrrCDlzc/yiKI3Ds5Ay6 mLBCCez+YX6qyTcqnbRRKbfsrqw7qLBmgYBF4xiAZe6Pyz9EqIriw25pBDPtPTEE/Qdz qnEkH7rdD0fFvTqVmw60/iaxPfAoJk/11e2SciYiTNadFZ+CD/kScq+LkStHiqtrXPTo krlFnJxBZxTw5kYIWlSc0HgXsKJzlPm8bXkGngrhBjvM/7b5zrAZ5Gd3kNKzKJINHXUQ aCDBIh6O/33E+Q6JmJNFbwdBim1RCLN5HrlS+vrQsd6tRG6rjxrbKqDudJu74QATSfNC VgDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1698285261; x=1698890061; h=content-transfer-encoding:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=IxyXRqXBDWI0lHk+KDRt8c4479uaLzWOf2qdkuFKABY=; b=eIQqpei5+zuLeDReuNusAWOqVc0OpvglEKL9Lrjz+cICs+iD1mjkEjx1mEbgJqckqr YVzOudeJ//QhoeuPCTQsDZvdxXg8618stQWfZuJbN4Ad/W1SgxEfBq9/L1BPrc7vI1mN Y17WJ4jtqENbl6dXyD2SIVy4GXp7TRP3d+xLNN3HAqO2YbtC3lyNjL7Se28hSIVTHk+T C5S7+t11+erv/h3BVfYJzRM5WXMx963LeaF/+FBvwRitCGKYyXCJEpxHmRq0ORlyjaYK pa/G7vk+bZnKq9fftoeaTEkSpWQLJOpLxoewpQdPLwE4hDP1UOHOLXvZZhS1A4uQIwqp IqSg== X-Gm-Message-State: AOJu0YzWuKjei4TeNwkQ+FhHoqpwCMBPh6s/01T2av3z/X2l2EUeDOFO 6lgHuOYg5c+iwxCzEeC+U9zU7OxzGkFYTz8B4VTm+OeoEjs= X-Google-Smtp-Source: AGHT+IG/UPnk4MwWnATnpYBtvst6W/jUlGC9XWrHncS1Z9X9qtT16C/sxxidxzghoTiDU5Etp+0BdTVQjmEVrxR9BYE= X-Received: by 2002:a50:cd1e:0:b0:53e:78ed:924d with SMTP id z30-20020a50cd1e000000b0053e78ed924dmr13917054edi.5.1698285260944; Wed, 25 Oct 2023 18:54:20 -0700 (PDT) MIME-Version: 1.0 References: <194372901-852eeb9299035adb7fdfc7fe5aa21080@pmq3v.m5r2.onet> In-Reply-To: From: Ethan Heilman Date: Wed, 25 Oct 2023 21:53:44 -0400 Message-ID: To: Steven Roose , Bitcoin Protocol Discussion Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: Re: [bitcoin-dev] Proposed BIP for OP_CAT 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: Thu, 26 Oct 2023 01:54:24 -0000 If there is sufficient interest in enabling OP_CAT on Bitcoin and there is a strong desire in the community for using OP_SUCCESS126 rather than OP_SUCCESS80 then I'd be happy to switch to OP_SUCCESS126. I don't have any particular affinity for OP_SUCCESS80. Is there anyone who objects to using OP_SUCCESS126 rather than OP_SUCCESS80= ? On Tue, Oct 24, 2023 at 4:12=E2=80=AFPM Steven Roose via bitcoin-dev wrote: > > I agree that there is no reason not to use OP_SUCCESS126, i.e. the origin= al OP_CAT opcode 0x7e. In many codebases, for example in Core, there might = be two OP_CAT constants than which might be confusing. > > On 10/22/23 09:58, vjudeu via bitcoin-dev wrote: > > > This opcode would be activated via a soft fork by redefining the opcode= OP_SUCCESS80. > > Why OP_SUCCESS80, and not OP_SUCCESS126? When there is some existing opco= de, it should be reused. And if OP_RESERVED will ever be re-enabled, I thin= k it should behave in the same way, as in pre-Taproot, so it should "Mark t= ransaction as invalid unless occuring in an unexecuted OP_IF branch". Which= means, " OP_VERIFY" should be equivalent to " OP_NOT= IF OP_RESERVED OP_ENDIF". > > > > On 2023-10-21 07:09:13 user Ethan Heilman via bitcoin-dev wrote: > > Hi everyone, > > We've posted a draft BIP to propose enabling OP_CAT as Tapscript opcode. > https://github.com/EthanHeilman/op_cat_draft/blob/main/cat.mediawiki > > OP_CAT was available in early versions of Bitcoin. It was disabled as > it allowed the construction of a script whose evaluation could create > stack elements exponential in the size of the script. This is no > longer an issue in the current age as tapscript enforces a maximum > stack element size of 520 Bytes. > > Thanks, > Ethan > > =3D=3DAbstract=3D=3D > > This BIP defines OP_CAT a new tapscript opcode which allows the > concatenation of two values on the stack. This opcode would be > activated via a soft fork by redefining the opcode OP_SUCCESS80. > > When evaluated the OP_CAT instruction: > # Pops the top two values off the stack, > # concatenate the popped values together, > # and then pushes the concatenated value on the top of the stack. > > OP_CAT fails if there are less than two values on the stack or if a > concatenated value would have a combined size of greater than the > maximum script element size of 520 Bytes. > > =3D=3DMotivation=3D=3D > Bitcoin tapscript lacks a general purpose way of combining objects on > the stack restricting the expressiveness and power of tapscript. For > instance this prevents among many other things the ability to > construct and evaluate merkle trees and other hashed data structures > in tapscript. OP_CAT by adding a general purpose way to concatenate > stack values would overcome this limitation and greatly increase the > functionality of tapscript. > > OP_CAT aims to expand the toolbox of the tapscript developer with a > simple, modular and useful opcode in the spirit of Unix[1]. To > demonstrate the usefulness of OP_CAT below we provide a non-exhaustive > list of some usecases that OP_CAT would enable: > > * Tree Signatures provide a multisignature script whose size can be > logarithmic in the number of public keys and can encode spend > conditions beyond n-of-m. For instance a transaction less than 1KB in > size could support tree signatures with a thousand public keys. This > also enables generalized logical spend conditions. [2] > * Post-Quantum Lamport Signatures in Bitcoin transactions. Lamport > signatures merely requires the ability to hash and concatenate values > on the stack. [3] > * Non-equivocation contracts [4] in tapscript provide a mechanism to > punish equivocation/double spending in Bitcoin payment channels. > OP_CAT enables this by enforcing rules on the spending transaction's > nonce. The capability is a useful building block for payment channels > and other Bitcoin protocols. > * Vaults [5] which are a specialized covenant that allows a user to > block a malicious party who has compromised the user's secret key from > stealing the funds in that output. As shown in A. Poelstra, "CAT > and Schnorr Tricks II", 2021, > https://www.wpsoftware.net/andrew/blog/cat-and-schnorr-tricks-ii.html > OP_CAT is sufficent to build vaults in Bitcoin. > * Replicating CheckSigFromStack A. Poelstra, "CAT and Schnorr > Tricks I", 2021, > https://medium.com/blockstream/cat-and-schnorr-tricks-i-faf1b59bd298 > which would allow the creation of simple covenants and other > advanced contracts without having to presign spending transactions, > possibly reducing complexity and the amount of data that needs to be > stored. Originally shown to work with Schnorr signatures, this result > has been extended to ECDSA signatures. [6] > > The opcode OP_CAT was available in early versions of Bitcoin. However > OP_CAT was removed because it enabled the construction of a script for > which an evaluation could have memory usage exponential in the size of > the script. > For instance a script which pushed an 1 Byte value on the stack then > repeated the opcodes OP_DUP, OP_CAT 40 times would result in a stack > value whose size was greater than 1 Terabyte. This is no longer an > issue because tapscript enforces a maximum stack element size of 520 > Bytes. > > =3D=3DSpecification=3D=3D > > Implementation > > if (stack.size() < 2) > return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION); > valtype vch1 =3D stacktop(-2); > valtype vch2 =3D stacktop(-1); > > if (vch1.size() + vch2.size() > MAX_SCRIPT_ELEMENT_SIZE) > return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION); > > valtype vch3; > vch3.reserve(vch1.size() + vch2.size()); > vch3.insert(vch3.end(), vch1.begin(), vch1.end()); > vch3.insert(vch3.end(), vch2.begin(), vch2.end()); > > popstack(stack); > popstack(stack); > stack.push_back(vch3); > > The value of MAX_SCRIPT_ELEMENT_SIZE is 520 Bytes =3D=3D Reference Implem= entation =3D=3D [Elements](https://github.com/ElementsProject/elements/blob= /master/src/script/interpreter.cpp#L1043) =3D=3DReferences=3D=3D [1]: R. Pi= ke and B. Kernighan, "Program design in the UNIX environment", 1983, https:= //harmful.cat-v.org/cat-v/unix_prog_design.pdf [2]: P. Wuille, "Multisig on= steroids using tree signatures", 2015, https://lists.linuxfoundation.org/p= ipermail/bitcoin-dev/2021-July/019233.html [3]: J. Rubin, "[bitcoin-dev] OP= _CAT Makes Bitcoin Quantum Secure [was CheckSigFromStack for Arithmetic Val= ues]", 2021, https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-J= uly/019233.html [4]: T. Ruffing, A. Kate, D. Schr=C3=B6der, "Liar, Liar, Co= ins on Fire: Penalizing Equivocation by Loss of Bitcoins", 2015, https://ci= teseerx.ist.psu.edu/viewdoc/download?doi=3D10.1.1.727.6262&rep=3Drep1&type= =3Dpdf [5]: M. Moser, I. Eyal, and E. G. Sirer, Bitcoin Covenants, http://f= c16.ifca.ai/bitcoin/papers/MES16.pdf [6]: R. Linus, "Covenants with CAT and= ECDSA", 2023, https://gist.github.com/RobinLinus/9a69f5552be94d13170ec79bf= 34d5e85#file-covenants_cat_ecdsa-md _______________________________________= ________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org htt= ps://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > > > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev