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Re: [Dcrup] rsa-sha1 usage

Phillip Hallam-Baker <phill@hallambaker.com> Wed, 14 June 2017 04:24 UTC

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From: Phillip Hallam-Baker <phill@hallambaker.com>
Date: Wed, 14 Jun 2017 00:24:47 -0400
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To: Scott Kitterman <sklist@kitterman.com>
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Subject: Re: [Dcrup] rsa-sha1 usage
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On Tue, Jun 13, 2017 at 11:28 PM, Scott Kitterman <sklist@kitterman.com> wrote:
>
>
> On June 13, 2017 11:20:42 PM EDT, Jim Fenton <fenton@bluepopcorn.net> wrote:

>>Based on no supporting data whatsoever, my conjecture is that
>>implementers pay a lot more attention to what RFCs say than people who
>>are deploying others' implementations. Which basically boils down to
>>MUSTs having a significant effect and SHOULDs having little. Which is
>>why I favor making signing with rsa-sha1 a MUST NOT prior to making
>>verification of rsa-sha1 signatures a MUST NOT.
>>
>>-Jim
>
> I agree on the importance of MUST versus SHOULD to implementors.  In general terms, MUST tells me what I have to implement and SHOULD tells me the defaults.
>
> I still think we should MUST NOT both signing and verification for rsa-sha1 if for no other reason than to not require implementations to support three algorithms, but I am starting to get the sense I'm in the rough on that.


It is a two step process in my view. First you rip out the generate,
then once the transition is complete, you rip out the accept.

SHA-1 is causing lots of issues as folk find 'funny' japes such as
bjorking GIT repos by uploading the pdf from the shattering. H(A1) =
H(A2) but H(Zip {A1, B, D, E, F}) <> H(Zip {A1, B, D, E, F})

Getting rid of SHA1 is the long term plan. But not in one go.

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