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From: Satoshin <satoshin@mybitcoincenter.com>
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Date: Tue, 22 Jan 2019 09:58:25 -0500
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To: ZmnSCPxj <ZmnSCPxj@protonmail.com>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Proof-of-Stake Bitcoin Sidechains
Precedence: list

This could could be a viable option. I think this is the right approach.

Any downside to this and how much does this add to the blockweight if =
anything at all.

Anonymouse

> On Jan 22, 2019, at 4:19 AM, ZmnSCPxj via bitcoin-dev =
<bitcoin-dev@lists.linuxfoundation.org> wrote:
>=20
> Good Morning Matt,
>=20
>> ### ZmnSCPxj,
>>=20
>> I'm intrigued by this mechanism of using fixed R values to prevent =
multiple signatures, but how do we derive the R values in a way where =
they are
> unique for each blockheight but still can be used to create signatures =
or verify?
>=20
> One possibility is to derive `R` using standard hierarchical =
derivation.
> Then require that the staking pubkey be revealed to the sidechain =
network as actually being `staking_pubkey =3D P + hash(P || parent_R) * =
G` (possibly with some trivial protection against Taproot).
> To sign for a blockheight `h`, you must use your public key `P` and =
the specific `R` we get from hierarchical derivation from `parent_R` and =
the blockheight as index.
>=20
>=20
>=20
> Regards,
> ZmnSCPxj
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