[cabfpub] Ballot 118 - SHA1 Sunset

Kelvin Yiu kelviny at exchange.microsoft.com
Tue Oct 7 18:27:45 UTC 2014

I think you have 2 problems when trying to support XP users after 1/1/2016:

1. Not being able to get new SHA1 SSL certificates that works on XP
2. Not being able to get new code signing certificates to sign new builds of Firefox, or sign Firefox in such a way that the same file will work on XP and the latest Windows release. 

Assuming you can workaround the first problem by finding a 1024 bit root CA that may or may not meet other security requirements, how will you deal with the 2nd problem?


-----Original Message-----
From: public-bounces at cabforum.org [mailto:public-bounces at cabforum.org] On Behalf Of Gervase Markham
Sent: Friday, October 3, 2014 3:24 AM
To: Ryan Sleevi
Subject: Re: [cabfpub] Ballot 118 - SHA1 Sunset

On 03/10/14 10:17, Ryan Sleevi wrote:
> It is worth noting that, according to Microsoft's policies (which, I 
> should note, Chrome has also adopted), no SHA-1 certs can be issued by 
> members of the root programs.

By CAs who are members of their root programs? Or by roots which are trusted by their root programs?

It might be possible to find a root, such as a 1024-bit one, which has been removed from root programs but is still trusted by the older browsers which such a scheme would target. Is there anything in Microsoft's or Google's policies which would prevent us asking a CA with such a root to issue us a SHA-1 certificate for the purpose of getting people onto software which supports SHA-256?

> However, I think you perhaps have too rosy a view about how such an 
> exemption would play out in practice. If browsers adopt negative UI 
> (as Chrome does, and as have both you and other Mozilla developers 
> suggested Firefox will/should) for such post-2016 certs, then the 
> ability to reasonably enforce such UI is contingent upon believing no 
> CAs will be issuing such certs.

Not really. Given that you are putting the UI in now, a row-back later would not have much immediate effect on the number of people who would get negative UI. Which would make a change of mind, even if you wanted one, impossible.

> The situation you describe - which doesn't arise until Jan 2016 -

Yes, indeed. But the de-adoption curves are not looking all that awesome.

> appetite for that. I think it's reasonable that by 2016, if you're 
> still running a 15 year old OS, you'll have a bad time. And not just 
> because SHA-1, but because SNI, ECDSA, etc.

Right. If we could get people to upgrade, we would.

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