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From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Fri, 22 Sep 2017 15:09:07 -0700
Message-ID: <CAPg+sBi+WnzpJkcG6XACdpqqz9ZA3rHX8+H9b5eExUdgXaeiWQ@mail.gmail.com>
To: Sergio Demian Lerner <sergio.d.lerner@gmail.com>, 
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Content-Type: multipart/alternative; boundary="94eb2c1282142deb0f0559ce7525"
Subject: Re: [bitcoin-dev] cleanstack alt stack & softfork improvements
 (Was: Merkle branch verification & tail-call semantics for generalized
 MAST)
Precedence: list

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On Fri, Sep 22, 2017 at 2:54 PM, Sergio Demian Lerner via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> If the variable size increase is only a few bytes, then three
> possibilities arise:
>
> - one should allow signatures to be zero padded (to reach the maximum
> size) and abandon strict DER encoding
>
> - one should allow spare witness stack elements (to pad the size to match
> the maximum size) and remove the cleanstack rule. But this is tricky
> because empty stack elements must be counted as 1 byte.
>
> - signers must loop the generation of signatures until the signature
> generated is of its maximum size.
>

Or (my preference);

- Get rid of DER encoding alltogether and switch to fixed size signatures.

Cheers,

-- 
Pieter

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<div dir=3D"ltr">On Fri, Sep 22, 2017 at 2:54 PM, Sergio Demian Lerner via =
bitcoin-dev <span dir=3D"ltr">&lt;<a href=3D"mailto:bitcoin-dev@lists.linux=
foundation.org" target=3D"_blank">bitcoin-dev@lists.linuxfoundation.org</a>=
&gt;</span> wrote:<br><div class=3D"gmail_extra"><div class=3D"gmail_quote"=
><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1=
px #ccc solid;padding-left:1ex"><div dir=3D"ltr">If the variable size incre=
ase is only a few bytes, then three possibilities arise:<div><br></div><div=
>- one should allow signatures to be zero padded (to reach the maximum size=
) and abandon strict DER encoding</div><div><br></div><div>- one should all=
ow spare witness stack elements (to pad the size to match the maximum size)=
 and remove the cleanstack rule. But this is tricky because empty stack ele=
ments must be counted as 1 byte.<div><br></div><div>- signers must loop the=
 generation of signatures until the signature generated is of its maximum s=
ize.</div></div></div></blockquote><div><br></div><div>Or (my preference);<=
/div><div><br></div><div>- Get rid of DER encoding alltogether and switch t=
o fixed size signatures.</div><div><br></div><div>Cheers,</div><div><br></d=
iv><div>-- <br></div><div>Pieter</div><div><br></div></div></div></div>

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