[cabfpub] To revoke or not to revoke 1024

Kathleen Wilson kwilson at mozilla.com
Mon Jun 24 22:31:32 UTC 2013


> Please comment, especially browser vendors.

Mozilla's wiki page about this (https://wiki.mozilla.org/CA:MD5and1024) 
was created in April 2010, and email about it was also sent to CAs 

The wiki page allows for use of 1024-bit certs when needed for 
interoperability reasons:
"- This means that CAs should only consider issuing a 1024-bit 
certificate if it is requested and justified by the subscriber for a 
specific reason, such as interoperability with devices that do not yet 
support certificates with larger key sizes.
- The CA must assess the risk involved in issuing such a certificate for 
legacy use/interoperability, and determine if they are willing to accept 
the risk, as well as any possible liability. The subject and relying 
parties also need to determine if they will accept any risks and 

The wiki page also makes it clear that CAs should not expect continued 
support of 1024-bit certs in Mozilla products:
"Under no circumstances should any party expect continued support for 
RSA key size smaller than 2048 bits past December 31, 2013."

> Do CAs need to revoke 1024-bit end-entity certs by the end of 2013?

I think that depends on the type of cert and when it expires.

I am fine with S/MIME certs being transitioned whenever they expire, 
even if it is a couple of years out. Though, I won't guarantee support 
of those certs in Mozilla products.

I would like to see the transition from 1024-bit SSL and code signing 
certs happen soon. However, it really doesn't matter to me what the 
exact date is, as long as the transition is completed before it becomes 
an emergency.

Also on the wiki page: "December 31, 2013 -- Mozilla will disable the 
SSL and Code Signing trust bits for root certificates with RSA key sizes 
smaller than 2048 bits. If those root certificates are no longer needed 
for S/MIME, then Mozilla will remove them from NSS."

In hindsight, I should have said "after December 31...". My goal is Q1 
2014, and I am working on this in Mozilla Bugzilla #881553.

> Since the BRs effectively cover only certs issued after "the effective 
> date", does that mean that certs issued before "the effective date" 
> don't need to be revoked?

That was my interpretation of the BRs, but Mozilla's communication about 
phasing out 1024-bit certs started in 2010. In 2010 I also exchanged 
direct email with representatives of the CAs that had 1024-bit root 
certs included in Mozilla products at that time, so all impacted CAs 
were well aware of Mozilla's requirements.

> What about code signing certs?

What I said above applies to both SSL and code signing certs.


On 6/23/13 12:32 PM, Rick Andrews wrote:
> We discussed this a bit in our face-to-face meeting in Munich, but did 
> not reach consensus. I'd like to continue the conversation with all 
> via the list.
> Putting aside the question of "web pki" vs. "non-web pki", Symantec 
> and other CAs would like to see if we can achieve consensus on these 
> questions:
>  1. Do CAs need to revoke 1024-bit end-entity certs by the end of 2013?
>  1. I believe that some CAs believed that revoking such certs was
>     mandatory. However, I see no hard evidence of that.
>  2. The BRs say that 1024-bit can be issued as long as the end date is
>     before December 31, 2013. Others have said that a CA that was
>     compliant with the BRs would not have issued a 1024-bit end entity
>     cert after the effective date if its end date was 2014 or later.
>     However, we've seen that not all CAs became compliant on July 1,
>     2012. Given what we now know about audits and effective dates, it
>     seems to me that there is a lot of uncertainty here.
>  3. Apart from the BRs, CAs have to consider browser policy which may
>     go above and beyond the BRs. In a private conversation with Tom
>     Albertson of Microsoft, he told me that "Our policy doesn't
>     contemplate CAs revoking EE certs issued before 1 Jan 2014, unless
>     or until an RSA factoring attack is imminent, and we all go into
>     response mode." Mozilla's policy seems to be similar -- it says
>     that such certs must expire by January 1, 2014, but it does not
>     mandate that CAs revoke any such certs that would live beyond that
>     date.
>  4. If there is no clear direction here, I propose that CAs simply let
>     all 1024-bit end entity certs expire naturally, as long as the CA
>     has stopped issuing 1024-bit end entity certs, and made an honest
>     effort to comply with the BRs (hard to define, but at the very
>     least would mean that the CA wasn't still issuing multi-year
>     1024-bit certs in 2013).
>  2. Since the BRs effectively cover only certs issued after "the
>     effective date", does that mean that certs issued before "the
>     effective date" don't need to be revoked?
>  5. That is my interpretation. Given what I said in 1) above, even
>     those certs issued after the effective date don't need to be
>     revoked, unless some browser's policy mandates that action.
>  3. What about code signing certs?
>  6. The BRs don't cover non-EV code signing certs, so again this goes
>     back to browser policy. And unless some browser comes forth with
>     unambiguous policy on code signing certs, I would suggest they are
>     also off the table (do not need to be revoked).
> Please comment, especially browser vendors. Thanks,
> -Rick
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