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From: Gregory Maxwell <greg@xiph.org>
To: "Артём Литвинович" <theartlav@gmail.com>,
	"Bitcoin Protocol Discussion"
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Why is deriving public key from the signature not used in Segwit?
Date: Wed, 24 Jan 2018 04:25:28 +0000	[thread overview]
Message-ID: <CAAS2fgQmKY5206-ko9ttV4K_4aPfoWh7Jrx=XYetXLeknU30iw@mail.gmail.com> (raw)
In-Reply-To: <CAJRVQkBPQR3Gz3AtWFgK_Z_9vDVZvR4Ws=f+tUZ3Y0mdswuk_g@mail.gmail.com>

On Wed, Jan 24, 2018 at 3:50 AM, Артём Литвинович via bitcoin-dev
<bitcoin-dev@lists.linuxfoundation.org> wrote:
> Greetings.
>
> I wanted to ask what was the rationale behind still having both public
> key and signature in Segwit witness?
>
> As is known for a while, the public key can be derived from the
> signature and a quadrant byte, a trick that is successfully used both
> in Bitcoin message signing algorithm and in Ethereum transaction
> signatures. The later in particular suggests that this is a perfectly
> functional and secure alternative.
> Leaving out the public key would have saved 33 bytes per signature,
> which is quite a lot.
>
> So, the question is - was there a good reason to do it the old way
> (security, performance, privacy, something else?), or was it something
> that haven't been thought of/considered at the time?

It is slow to verify, incompatible with batch validation, doesn't save
space if hashing isn't used, and is potentially patent encumbered.


  reply	other threads:[~2018-01-24  4:25 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-24  3:50 [bitcoin-dev] Why is deriving public key from the signature not used in Segwit? Артём Литвинович
2018-01-24  4:25 ` Gregory Maxwell [this message]
2018-01-24 10:24   ` Aymeric Vitte
2018-01-24 10:31     ` Gregory Maxwell
2018-01-24 11:16       ` Aymeric Vitte
2018-01-24 11:35         ` Gregory Maxwell
2018-01-24 12:03           ` Aymeric Vitte

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