Re: [TLS] New directions in certificate status

[Phillip Hallam-Baker <[e-mail]>]

On Fri, Oct 10, 2014 at 11:51 AM, Viktor Dukhovni
<[e-mail]> wrote:
> On Fri, Oct 10, 2014 at 03:32:05PM +0100, Rob Stradling wrote:
>
>> Size of the resulting "Compressed CRLSet": ~182K
>>
>> That's ~6 bits per unexpired-and-revoked-and-publicly-trusted TLS Server
>> Certificate.
>
> Is this compressed across multiple issuing CAs?  If so who signs
> the validity of such a list?  Is the expectation that CRLs will be
> vetted and curated by browser vendors (with frequent updates over
> a suitably secure channel)?

It could be applied either way.

In fact this is part of what we need to discuss going forward because
there is more than one way we could deploy this technology.

One big CRL is one option. Separate CRLs produced by each CA is
another. A third possibility is we join separate CRLs into one large
distribution.

Given that we are already looking at TRANS deployment we might well
want to consider a mechanism that streamlines deployment of both.


> How does this interact with intramural CRLs maintained by organizations
> on their non-public internal networks?  I am guessing this would
> be a complementary mechanism.

I would have to think rather hard about that case. One side effect of
this technology is that the CRL leaks less information than a
traditional one. If all you have is a compressed CRL then you know the
number of revoked certs but you don't know very much about any of
them. A traditional CRL tells you all the serial numbers which might
well leak rather a lot of data.


> If this is frequently updated data, would it not be more efficient
> to just send the newly expired (CA, serial) pairs when updating,
> rather than compressing the whole set.  At which point how important
> is the initial compression?

Delta CRLs have been tried in the past. The problem is that the
relying party still needs to store the serial number of every revoked
certificate. And it gets worse because it is harder to purge the list
for expired certs.