Date: Mon, 05 Jul 2021 02:39:08 +0000
To: Russell O'Connor <roconnor@blockstream.com>
From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Reply-To: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Message-ID: <l_aP9orUBtFIl4MZp7uritXRqdvsn-ZwC1LhVLwHXIiE8FNShKcbKtapcjvb92HEl1liepJSG1UYtrQW-qMSQnecCcQnf_HHkcVuWhvm1g4=@protonmail.com>
In-Reply-To: <CAMZUoKnjAd8hUpa5nZyPWTx_uxHtLL8XOjbROxobfAC+6yMWUA@mail.gmail.com>
References: <CAD5xwhjmu-Eee47Ho5eA6E6+aAdnchLU0OVZo=RTHaXnN17x8A@mail.gmail.com>
 <20210704011341.ddbiruuomqovrjn6@ganymede>
 <CAD5xwhimPBEV_tLpSPxs9B+XGUhvPx_dnhok=8=hyksyi4=B6g@mail.gmail.com>
 <20210704203230.37hlpdyzr4aijiet@ganymede>
 <5keA_aPvmCO5yBh_mBQ6Z5SwnnvEW0T-3vahesaDh57f-qv4FbG1SFAzDvT3rFhre6kFl282VsxV_pynwn_CdvF7fzH2q9NW1ZQHPH1pmdo=@protonmail.com>
 <CAMZUoKnVLRLgL1rcq8DYHRjM--8VEUC5kjUbzbY5S860QSbk5w@mail.gmail.com>
 <CAMZUoKnjAd8hUpa5nZyPWTx_uxHtLL8XOjbROxobfAC+6yMWUA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Unlimited covenants,
	was Re: CHECKSIGFROMSTACK/{Verify} BIP for Bitcoin
Precedence: list

Good morning Russell,


> On Sun, Jul 4, 2021 at 9:02 PM Russell O'Connor <roconnor@blockstream.com=
> wrote:
>
> > Bear in mind that when people are talking about enabling covenants, we =
are talking about whether OP_CAT should be allowed or not.
> >
> > That said, recursive covenants, the type that are most worrying, seems =
to require some kind of OP_TWEAK operation, and I haven't yet seen any evid=
ence that this can be simulated with CHECKSIG(FROMSTACK).=C2=A0 So maybe we=
 should leave such worries for the OP_TWEAK operation.
>
> Upon further thought, you can probably make recursive covenants even with=
 a fixed scritpubkey by sneaking the state into a few bits of the UTXO's am=
ount.=C2=A0 Or if you try really hard, you may be able to stash your state =
into a sibling output that is accessed via the txid embedded in the prevout=
point.

Which is kind of the point of avoiding giving too much power, because peopl=
e can be very clever and start doing unexpected things from what you think =
is already a limited subset.
"Give an inch and they will take a mile".

Still, as pointed out, altcoins already exist and are substantially worse, =
and altcoin implementations are all going to run on Turing machines anyway =
(which are powerful enough to offer Turing-machine functionality), so maybe=
 this is not really giving too much power, people can already fork Bitcoin =
and add full EVM support on it.

Regards,
ZmnSCPxj