Re: [openpgp] V5 Fingerprint again

On Wed, Mar 01, 2017 at 07:12:20PM -0500, Derek Atkins wrote:
> On  Wed, Mar 1, 2017 6:27 PM, Leo Gaspard <leo@gaspard.io> wrote:
> > On 03/01/2017 06:30 PM, Phillip Hallam-Baker wrote:
> > > H(x) = SHA-2-512(x)
> > 
> > Hoping this hasn't been discussed before, but... is there a reason for
> > not picking SHA3-512? (or SHAKE256 with 25*8 bits of output if willing
> > to stay at 25 octets for the fingerprint)
>
> Because the SHA3 competition showed us that SHA2 is a good hash...  and SHA2 is much faster than SHA3.

BLAKE2 is faster than either (2-3× faster than SHA-2, depending on configuration,
and about 3-5× faster than SHA-3), and designed for ease-of-implementation on a
variety of platforms, and was standardized as [RFC 7693].

It's widely-regarded as secure; quoting the SHA-3 final report [0]:

> BLAKE and Keccak have very large security margins. [...]
> Skein and BLAKE have no known distinguishing attacks that come close to threatening their
> full-round versions.  Grøstl, Skein, and BLAKE have a large number of attack papers reflecting
> considerable depth of analysis.

Moreover, quite a few projects already picked it as their hash function of
choice, due to said advantages, so there is existing library support and
we can likely expect that to be true for quite some time.

In that context, is there something I missed which says
we can't have our cake and eat it too?

Best,

  kf

[0]: http://nvlpubs.nist.gov/nistpubs/ir/2012/NIST.IR.7896.pdf
[RFC 7693]: https://tools.ietf.org/html/rfc7693

> 
> -derek
> 
> Sent from my mobile device. Please excuse any typos.
> 
> ----- Reply message -----
> From: "Leo Gaspard" <leo@gaspard.io>
> To: <openpgp@ietf.org>
> Subject: [openpgp] V5 Fingerprint again
> Date: Wed, Mar 1, 2017 6:27 PM
> 
> On 03/01/2017 06:30 PM, Phillip Hallam-Baker wrote:
> > H(x) = SHA-2-512(x)
> 
> Hoping this hasn't been discussed before, but... is there a reason for
> not picking SHA3-512? (or SHAKE256 with 25*8 bits of output if willing
> to stay at 25 octets for the fingerprint)
> 
> This should push back the next required switch to a v6 key.

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