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 9D046C000E for ; Tue, 6 Jul 2021 11:26:41 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 7F93D8376D for ; Tue, 6 Jul 2021 11:26:41 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org X-Spam-Flag: NO X-Spam-Score: -1.899 X-Spam-Level: X-Spam-Status: No, score=-1.899 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no Authentication-Results: smtp1.osuosl.org (amavisd-new); dkim=pass (2048-bit key) header.d=blockstream-com.20150623.gappssmtp.com 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 w17D2OBOd44g for ; Tue, 6 Jul 2021 11:26:40 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.8.0 Received: from mail-qk1-x72b.google.com (mail-qk1-x72b.google.com [IPv6:2607:f8b0:4864:20::72b]) by smtp1.osuosl.org (Postfix) with ESMTPS id 62ADA83750 for ; Tue, 6 Jul 2021 11:26:40 +0000 (UTC) Received: by mail-qk1-x72b.google.com with SMTP id g4so19771027qkl.1 for ; Tue, 06 Jul 2021 04:26:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=blockstream-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=eacrwN+kD9OCFqE4loeIt0N9icanT+hhr5TNJGJifak=; b=u56kFhhfqmNAr+EMRqHs0K85VszIkfXSBuuV9YPQKoaKKk6r8mP+oiy5GhmVIAucFF 71vZX71JvwSvn2ACmZFbLM7qFRFMoukaXbsG6PHtgwd83X5UY0n6vZd35Ur5VTbqV5AG Bo7ye6FhZQdMpB5Yp26Qwaa4wEInuVKLZ6NKkEOEZlNxnuMnFFO+HjPf+GPsUe5e8SaL NnNlquNnfHJZe0kS120kfdJkuyP9w2Ez33ov0ju0FOzbX+v6YHQ1Ggc+4opafUCbZVxz moDam5wYz2JRZOdL1pxqw5864xHpqaHlI2tzE/AQvZ6pUgqj/X1a31FA6aGWLS9CB7B7 OLHA== 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; bh=eacrwN+kD9OCFqE4loeIt0N9icanT+hhr5TNJGJifak=; b=PBSkmFG3tmTtKdsmKOq9MrsENyZ4eE4TKxynST/O7dPkDoNtLVdo6Idt0blbMLoDZU 2EGQf/q6XdSbT2G9LT/phkrkwb3h/urOBt2HZw70yhY29z1fV5R73H1ID4Wva1bx03zf EH0c+htmhkHsTh8u31zxmB+Wq9QeEYKkoBfMHDOD3xgR4logwFyzm+OtE7eVhhMcb2BN ri5kORiyEJ5eEJrsz3V57F/16AmS3ANAiTghl1g1hnfngivxq+JXNV7KDjPS7cpSfiS4 XDvGQ6jJUxd9XtCTstWFLCI4X9ZkqNv4oqHlH5nebuiRBzHVWuyy1tw5iqhhf+lpaP7t njIw== X-Gm-Message-State: AOAM53338tsKoLz5jLZIhLA6vQH0w3QGwLqX9NwyIvffTxysI+rDXbmy vX0p0Nc9xn0aQIMJvKPCcDKNd47thM/PVVNSjE8djw== X-Google-Smtp-Source: ABdhPJwad7nOhYdn3h1jZR0G+imqSAua8lPSm7wai+tLDGWLlVtHLM+qXfAoh1Lv5rnTuPVbplaSupQxeMdS3QkaNZ0= X-Received: by 2002:a37:9606:: with SMTP id y6mr19248767qkd.13.1625570799152; Tue, 06 Jul 2021 04:26:39 -0700 (PDT) MIME-Version: 1.0 References: <20210704011341.ddbiruuomqovrjn6@ganymede> <20210704203230.37hlpdyzr4aijiet@ganymede> <5keA_aPvmCO5yBh_mBQ6Z5SwnnvEW0T-3vahesaDh57f-qv4FbG1SFAzDvT3rFhre6kFl282VsxV_pynwn_CdvF7fzH2q9NW1ZQHPH1pmdo=@protonmail.com> In-Reply-To: From: "Russell O'Connor" Date: Tue, 6 Jul 2021 07:26:28 -0400 Message-ID: To: Billy Tetrud Content-Type: multipart/alternative; boundary="0000000000000a849f05c672b2e4" Cc: Bitcoin Protocol Discussion Subject: Re: [bitcoin-dev] Unlimited covenants, was Re: CHECKSIGFROMSTACK/{Verify} BIP for Bitcoin 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: Tue, 06 Jul 2021 11:26:41 -0000 --0000000000000a849f05c672b2e4 Content-Type: text/plain; charset="UTF-8" On Tue, Jul 6, 2021 at 2:26 AM Billy Tetrud wrote: > > when people are talking about enabling covenants, we are talking about > whether OP_CAT should be allowed or not > > Are they? Are you implying that anything that enables covenants is > equivalent to enabling OP_CAT? Generally when I think about enabling > covenants, I'm thinking more about OP_CTV (or some similarly specific > opcode > > ). > > > OP_TWEAK > > I wasn't able to find anything about what that is. Would you mind > clarifying what that concept is? > In tapscript one can generally recover the current input's scriptPubkey through sighash introspection via the usual covenant tricks. This allows you to make a recursive covenant by spending funds back to the same identical scriptPubkey. However, in order for a recursive covenant to be actually interesting, there needs to be some sort of state update in each transition. If there is no state update then sending funds back to itself is of very limited value. It will reset the timer on relative locks, but that is about all. The "normal" way of writing useful recursive covenants is to modify the scriptPubkey by changing a fragment of it that contains some sort of state. However in order to update a tapscript pubkey one needs to apply not only hashing, to create a Merkel root, but also to create a tweaked taproot pubkey that commits to this root. While script currently comes with a SHA-256 hashing opcode, there is no opcode that will let you perform the necessary tweaking to create a taproot scriptPubkey. But as I mentioned afterwards, there are other places in the UTXO that you could put data in order to perform a state update. --0000000000000a849f05c672b2e4 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Tue, Jul 6, 2021 at 2:26 AM Billy Tetrud <billy.tetrud@gmail.com> wrote:
>=C2=A0 when people are talking about enabling covenants, we are talking about whet= her OP_CAT should be allowed or not

Are they? Are you im= plying that anything that enables covenants is equivalent to enabling OP_CA= T? Generally when I think about enabling covenants, I'm thinking more a= bout OP_CTV (or some similarly specific opcode).

> OP_TWEAK=C2=A0=

I wasn't able to find anything about=C2=A0wha= t that is. Would you mind clarifying what that concept is?
=

In tapscript one can generally recover the= current input's scriptPubkey through sighash introspection via the usu= al covenant tricks.=C2=A0 This allows you to make a recursive covenant by s= pending funds back to the same identical scriptPubkey.=C2=A0 However, in or= der for a recursive covenant to be actually interesting, there needs to be = some sort of state update in each transition.=C2=A0 If there is no state up= date then sending funds back to itself is of very limited value.=C2=A0 It w= ill reset the timer on relative locks, but that is about all.
The "normal" way of writing useful recursive covenant= s is to modify the scriptPubkey by changing a fragment of it that contains = some sort of state.=C2=A0 However in order to update a tapscript pubkey one= needs to apply not only hashing, to create a Merkel root, but also to crea= te a tweaked taproot pubkey that commits to this root.=C2=A0 While script c= urrently comes with a SHA-256 hashing opcode, there is no opcode that will = let you perform the necessary tweaking to create a taproot scriptPubkey.

But as I mentioned afterwards, there are other place= s in the UTXO that you could put data in order to perform a state update.
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