From ZmnSCPxj at protonmail.com  Tue Dec 17 15:14:50 2019
From: ZmnSCPxj at protonmail.com (ZmnSCPxj)
Date: Tue, 17 Dec 2019 15:14:50 +0000
Subject: [Lightning-dev] Pay-to-Open and UX improvements
In-Reply-To: <20191217144346.erlikoqqllxu4irx@ganymede>
References: <CACdvm3O5oXcEspx1Vu-ioCw=JZMQmMKsUYFsX9q1GHnXGce_wQ@mail.gmail.com>
 <20191217144346.erlikoqqllxu4irx@ganymede>
Message-ID: <3GiEjMd49K1cZukcBKrRpZE4xa0-GQ4andCz_4MIO3WHIjSdDEdPrOTwez7hJwHgHM9NUHzXaWoSGPd6m_71xoLJvZUEw1Cllcm6TfFb5Yo=@protonmail.com>

Good morning David, t-bast, and all,


> I'm not aware of any way to currently force single-show signatures in
> Bitcoin, so this is pretty theoretical. Also, single-show signatures
> add a lot of fragility to any setup and make useful features like RBF
> fee bumping unavailable.

With `OP_CAT`, we can enforce that a particular `R` is used, which allows to implement single-show signatures.

    # Assuming signatures are the concatenation of (R,s)
    <R> OP_SWAP OP_CAT <ACINQ> OP_CHECKSIG

The above would then feed `s` only on the witness stack.

Regards,
ZmnSCPxj