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From: Arthur Chen <arthur.chen@btcc.com>
Date: Mon, 4 Jul 2016 01:23:14 +0000
Message-ID: <CAP+0UNJ9mBCWCNf_kSo+4xJWjmO=eVmrrRi7=dD9_zmU2h3cDw@mail.gmail.com>
To: Zooko Wilcox <zooko@z.cash>, 
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Content-Type: multipart/alternative; boundary=001a113d7f1432a0900536c52ecf
Subject: Re: [bitcoin-dev] BIP 151 use of HMAC_SHA512
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I strongly agree!
In crypto we should always follow well-studied open standard rather than
custom construction.

On Fri, Jul 1, 2016 at 10:42 PM, Zooko Wilcox via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> I haven't been able to find the beginning of this thread, so apologies
> if I've misunderstood what this is for, but it _sounds_ like we're
> re-inventing HKDF.
>
> I'd recommend reading the paper about HKDF. It stands out among crypto
> papers for having a nice clear justification for each of its design
> decisions, so you can see why they did it (very slightly) differently
> than the various constructions proposed up-thread.
>
> https://eprint.iacr.org/2010/264
>
> Also, of course, it is a great idea to re-use a standard
> (https://tools.ietf.org/html/rfc5869) and widely-understood crypto
> algorithm to reduce risk of both cryptographer errors and implementor
> errors.
>
> Of course, the cost of that is the you sometimes end up computing
> something that is a tiny bit more complicated or inefficient than a
> custom algorithm for our current use case. IMHO that's a cheap price
> to pay.
>
> Regards,
>
> Zooko
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>


-- 
Xuesong (Arthur) Chen
Senior Principle Engineer
BlockChain Technologist
BTCC

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<div dir=3D"ltr"><div>I strongly agree!<br></div>In crypto we should always=
 follow well-studied open standard rather than custom construction.<br></di=
v><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Fri, Jul 1, =
2016 at 10:42 PM, Zooko Wilcox via bitcoin-dev <span dir=3D"ltr">&lt;<a hre=
f=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blank">bitcoi=
n-dev@lists.linuxfoundation.org</a>&gt;</span> wrote:<br><blockquote class=
=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padd=
ing-left:1ex">I haven&#39;t been able to find the beginning of this thread,=
 so apologies<br>
if I&#39;ve misunderstood what this is for, but it _sounds_ like we&#39;re<=
br>
re-inventing HKDF.<br>
<br>
I&#39;d recommend reading the paper about HKDF. It stands out among crypto<=
br>
papers for having a nice clear justification for each of its design<br>
decisions, so you can see why they did it (very slightly) differently<br>
than the various constructions proposed up-thread.<br>
<br>
<a href=3D"https://eprint.iacr.org/2010/264" rel=3D"noreferrer" target=3D"_=
blank">https://eprint.iacr.org/2010/264</a><br>
<br>
Also, of course, it is a great idea to re-use a standard<br>
(<a href=3D"https://tools.ietf.org/html/rfc5869" rel=3D"noreferrer" target=
=3D"_blank">https://tools.ietf.org/html/rfc5869</a>) and widely-understood =
crypto<br>
algorithm to reduce risk of both cryptographer errors and implementor<br>
errors.<br>
<br>
Of course, the cost of that is the you sometimes end up computing<br>
something that is a tiny bit more complicated or inefficient than a<br>
custom algorithm for our current use case. IMHO that&#39;s a cheap price<br=
>
to pay.<br>
<br>
Regards,<br>
<br>
Zooko<br>
<div class=3D"HOEnZb"><div class=3D"h5">___________________________________=
____________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.=
linuxfoundation.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.org/mail=
man/listinfo/bitcoin-dev</a><br>
</div></div></blockquote></div><br><br clear=3D"all"><br>-- <br><div class=
=3D"gmail_signature" data-smartmail=3D"gmail_signature"><div dir=3D"ltr">Xu=
esong (Arthur) Chen<div>Senior Principle Engineer</div><div>BlockChain Tech=
nologist</div><div>BTCC</div></div></div>
</div>

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