Policy For Sunsetting GPG Keys < 2048 Bits

[Kees Cook]

On Wed, Nov 26, 2014 at 06:09:41PM -0500, Scott Kitterman wrote:
> As many of you know, Debian is in the process of terminating use of 1024 bit 
> keys due to near term security concerns [1].  In Ubuntu, we should probably do 
> this too, but since any developer can replace an existing key via the 
> Launchpad U/I and there's no requirement to get keys signed through web of 
> trust, we ought to be able to do it much faster.
> 
> Some data [2]
> 
> Ubuntu has a total of 207 uploaders.
> Ubuntu has a total of 314 GPG keys with upload privileges tied to them.
> 
> Here are rough status on the number of primary and sub-keys and their sizes:
> 
>     119 pub   dsa1024
>       2 pub   dsa3072
>       1 pub   dsa768
>       2 pub   rsa1024
>       1 pub   rsa10240
>       1 pub   rsa2047
>      56 pub   rsa2048
>       1 pub   rsa3072
>     120 pub   rsa4096
>       1 pub   rsa8192
>       1 sub   dsa3072
>      27 sub   elg1024
>       2 sub   elg1536
>      71 sub   elg2048
>      16 sub   elg4096
>       1 sub   elg768
>       9 sub   rsa1024
>       1 sub   rsa10240
>      66 sub   rsa2048
>       8 sub   rsa3072
>       1 sub   rsa4064
>     112 sub   rsa4096
> 
> While this does affect a significant number of keys, it's easy for people to 
> upgrade, so this transition doesn't have to take a long time.  On IRC 
> (#ubuntu-release) we discussed the idea of, once a policy is decided on, 
> having a U-D-A announcement, followed by individual nag mails, and warnings 
> after uploads with keys that are about to be disabled.  There was some 
> discussion about if PPAs should have the same restriction or now.
> 
> Discuss...

I think we should have the same policy for PPAs, and it should follow the
same timeline. Additionally, we should have LP reject uploading weak keys,
which could happens early in the transition timeline.

(Seems like we should ditch DSA keys entirely, and all RSA less than 2048.)

-Kees

> 
> Scott K
> 
> [1] https://lists.debian.org/debian-devel-announce/2014/11/msg00004.html
> [2] Thanks to stgraber, xnox, and wgrant
> 
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-- 
Kees Cook