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From: Arthur Chen <arthur.chen@btcc.com>
Date: Tue, 28 Jun 2016 16:31:51 +0800
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Subject: Re: [bitcoin-dev] BIP 151 use of HMAC_SHA512
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Based on previous crypto analysis result, the actual security of SHA512 is
not significantly higher than SHA256.
maybe we should consider SHA3?
On Tue, Jun 28, 2016 at 3:19 PM, Jonas Schnelli via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:
> > To quote:
> >
> >> HMAC_SHA512(key=ecdh_secret|cipher-type,msg="encryption key").
> >>
> >> K_1 must be the left 32bytes of the HMAC_SHA512 hash.
> >> K_2 must be the right 32bytes of the HMAC_SHA512 hash.
> >
> > This seems a weak reason to introduce SHA512 to the mix. Can we just
> > make:
> >
> > K_1 = HMAC_SHA256(key=ecdh_secret|cipher-type,msg="header encryption
> key")
> > K_2 = HMAC_SHA256(key=ecdh_secret|cipher-type,msg="body encryption key")
>
> SHA512_HMAC is used by BIP32 [1] and I guess most clients will somehow
> make use of bip32 features. I though a single SHA512_HMAC operation is
> cheaper and simpler then two SHA256_HMAC.
>
> AFAIK, sha256_hmac is also not used by the current p2p & consensus layer.
> Bitcoin-Core uses it for HTTP RPC auth and Tor control.
>
> I don't see big pros/cons for SHA512_HMAC over SHA256_HMAC.
>
> </jonas>
>
> [1]
>
> https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki#child-key-derivation-ckd-functions
>
>
> _______________________________________________
> 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
--001a113d7f14f9d4c905365277d8
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr">Based on previous crypto analysis result, the actual secur=
ity of SHA512 is not significantly higher than SHA256.<div>maybe we should =
consider SHA3?<br><div><br></div></div></div><div class=3D"gmail_extra"><br=
><div class=3D"gmail_quote">On Tue, Jun 28, 2016 at 3:19 PM, Jonas Schnelli=
via bitcoin-dev <span dir=3D"ltr"><<a href=3D"mailto:bitcoin-dev@lists.=
linuxfoundation.org" target=3D"_blank">bitcoin-dev@lists.linuxfoundation.or=
g</a>></span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margi=
n:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=3D"">=
> To quote:<br>
><br>
>> HMAC_SHA512(key=3Decdh_secret|cipher-type,msg=3D"encryption k=
ey").<br>
>><br>
>>=C2=A0 K_1 must be the left 32bytes of the HMAC_SHA512 hash.<br>
>>=C2=A0 K_2 must be the right 32bytes of the HMAC_SHA512 hash.<br>
><br>
> This seems a weak reason to introduce SHA512 to the mix.=C2=A0 Can we =
just<br>
> make:<br>
><br>
> K_1 =3D HMAC_SHA256(key=3Decdh_secret|cipher-type,msg=3D"header e=
ncryption key")<br>
> K_2 =3D HMAC_SHA256(key=3Decdh_secret|cipher-type,msg=3D"body enc=
ryption key")<br>
<br>
</span>SHA512_HMAC is used by BIP32 [1] and I guess most clients will someh=
ow<br>
make use of bip32 features. I though a single SHA512_HMAC operation is<br>
cheaper and simpler then two SHA256_HMAC.<br>
<br>
AFAIK, sha256_hmac is also not used by the current p2p & consensus laye=
r.<br>
Bitcoin-Core uses it for HTTP RPC auth and Tor control.<br>
<br>
I don't see big pros/cons for SHA512_HMAC over SHA256_HMAC.<br>
<br>
</jonas><br>
<br>
[1]<br>
<a href=3D"https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki#c=
hild-key-derivation-ckd-functions" rel=3D"noreferrer" target=3D"_blank">htt=
ps://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki#child-key-deriv=
ation-ckd-functions</a><br>
<br>
<br>_______________________________________________<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>
<br></blockquote></div><br><br clear=3D"all"><div><br></div>-- <br><div cla=
ss=3D"gmail_signature" data-smartmail=3D"gmail_signature"><div dir=3D"ltr">=
Xuesong (Arthur) Chen<div>Senior Principle Engineer</div><div>BlockChain Te=
chnologist</div><div>BTCC</div></div></div>
</div>
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