Re: Hash algorithm analysis

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On Sat, 21 Jul 2018 23:59:41 +0000, brian m. carlson wrote:
> On Sun, Jul 22, 2018 at 12:38:41AM +0200, Johannes Schindelin wrote:
> > Do you really want to value contributors' opinion more than
> > cryptographers'? I mean, that's exactly what got us into this hard-coded
> > SHA-1 mess in the first place.
> 
> I agree (believe me, of all people, I agree) that hard-coding SHA-1 was
> a bad choice in retrospect.  But I've solicited contributors' opinions
> because the Git Project needs to make a decision *for this project*
> about the algorithm we're going to use going forward.
> 
> > And to set the record straight: I do not have a strong preference of the
> > hash algorithm. But cryprographers I have the incredible luck to have
> > access to, by virtue of being a colleague, did mention their preference.
> 
> I don't know your colleagues, and they haven't commented here.  One
> person that has commented here is Adam Langley.  It is my impression
> (and anyone is free to correct me if I'm incorrect) that he is indeed a
> cryptographer.  To quote him[0]:
> 
>   I think this group can safely assume that SHA-256, SHA-512, BLAKE2,
>   K12, etc are all secure to the extent that I don't believe that making
>   comparisons between them on that axis is meaningful. Thus I think the
>   question is primarily concerned with performance and implementation
>   availability.
> 
>   […]
> 
>   So, overall, none of these choices should obviously be excluded. The
>   considerations at this point are not cryptographic and the tradeoff
>   between implementation ease and performance is one that the git
>   community would have to make.

  Am I completely out of the game, or the statement that
    "the considerations at this point are not cryptographic"
  is just the wrongest ?

  I mean, if that was true, would we not be sticking to SHA1 ?

> I'm aware that cryptographers tend to prefer algorithms that have been
> studied longer over ones that have been studied less.  They also prefer
> algorithms built in the open to ones developed behind closed doors.
> 
> SHA-256 has the benefit that it has been studied for a long time, but it
> was also designed in secret by the NSA.  SHA3-256 was created with
> significant study in the open, but is not as mature.  BLAKE2b has been
> incorporated into standards like Argon2, but has been weakened slightly
> for performance.
> 
> I'm not sure that there's a really obvious choice here.
> 
> I'm at the point where to continue the work that I'm doing, I need to
> make a decision.  I'm happy to follow the consensus if there is one, but
> it does not appear that there is.
> 
> I will admit that I don't love making this decision by myself, because
> right now, whatever I pick, somebody is going to be unhappy.  I want to
> state, unambiguously, that I'm trying to make a decision that is in the
> interests of the Git Project, the community, and our users.
> 
> I'm happy to wait a few more days to see if a consensus develops; if so,
> I'll follow it.  If we haven't come to one by, say, Wednesday, I'll make
> a decision and write my patches accordingly.  The community is free, as
> always, to reject my patches if taking them is not in the interest of
> the project.
> 
> [0] https://public-inbox.org/git/CAL9PXLzhPyE+geUdcLmd=pidT5P8eFEBbSgX_dS88knz2q_LSw@xxxxxxxxxxxxxx/
> -- 
> brian m. carlson: Houston, Texas, US
> OpenPGP: https://keybase.io/bk2204



-- 
  Eric Deplagne

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