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Re: The SHA1 sunset
Re: The SHA1 sunset
Tue, 05 Jan 2016 01:38:06 -0500
Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux)
On Mon, Jan 04, 2016 at 23:14:06 +0100, Lars Magne Ingebrigtsen wrote:
> I'm not sure why you're linking to that site?
This was the recent paper describing the only SHA-1 collision which was
directly addressed in Ballot 152 in determining whether to continue
issuing SHA-1 certs through 2016:
> The question isn't whether the NSA are able to do SHA-1 collisions
> (which I think everybody assumes that they can, albeit expensively), but
> whether they can create certificates. The jury is out on that one, and
> many people think that it's not a thing (yet) (with certificates with
> the recommended entropy in serial numbers and dates).
That's all good when those suggestions are actually implemented.
>> Such a warning will not be bogus, and it would be a service to warn
>> users even if others don't.
> It will almost certainly be bogus (now). Next year, perhaps not.
SHA-1 is broken, which we can agree on. The proposal by CloudFlare to
randomize serial numbers with at least 20 bits of entropy is a band aid
atop of a broken cryptosystem. It should work for the meantime---for
those CAs that actually implement it---but
this is not an alternative to issuing SHA-2 certificates, and it won't
help already issued certs. Personally, I prefer not to rely on bandages
for my crypto.
Since this mitigation attempt is dependent on CAs adopting it, that can
only get _better_ with time. Considering SHA-1 to be broken (period),
then presumably, a year from now, we'd only be in a better position if
new SHA-1 certs are issued with a randomized serial number, given the
relative increase in computing cost/power. We would be in a worse
position for SHA-1 certs that haven't expired a year from now, since
they'll be cheaper to exploit.
CloudFlare also wrote about browser support for SHA-2:
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Re: The SHA1 sunset, James Cloos, 2016/01/04