Re: mail signing history, was Call for Community Feedback: Retiring IETF FTP Service

[Michael Thomas <[e-mail]>]

On 11/18/20 2:04 PM, Stephen Farrell wrote:
>
> Hiya,
>
> On 18/11/2020 21:51, Michael Thomas wrote:
>>
>> On 11/18/20 1:45 PM, John R Levine wrote:
>>> On Wed, 18 Nov 2020, Ned Freed wrote:
>>>> That said, a mechanism for publishing/expiring DKIM private keys is 
>>>> something
>>>> the IETF might want to standardize.
>>>
>>> I've started to publish my old private keys since I rotate every 
>>> month but I agree a standard way to tell people where to look would 
>>> be nice.
>>>
>> Why isn't just deleting/replacing the selector sufficient? It's not 
>> as definitive but it's a lot simpler.
>
> Publishing the private key enables various forms of
> denyability - if someone claims msg1 is original
> anyone with access to the private can produce a
> msg2 that seems as cryptographically correct but
> is clearly bogus (e.g. containing lottery numbers
> that post-date message timestamps).


Yes, i acknowledge that above albeit obliquely. What i don't see is how 
you align providers goals' with individual users' goals.


>
> Yes an adversary could have gotten an independent
> signed timestamp on msg1 before the private was
> published but that seems low probability.
It really depends on the worth of the data, right? LEA would certainly 
do such a thing if they were serveilling somebody.
>
> I'd support development of such a standard if it
> had a good chance of deployment as I think it'd
> also encourage key rotation.
>
I forget who said that they were surprised about lack of key rotation, 
but color me completely unsurprised. This is just inertia 101. Maybe 
large ESP's might get around to automating key rotation, but for the 
vast majority enterprise this is going to be pretty low down the 
priority list, and more likely an anti-goal as tracking whether their 
employees are misbehaving is a feature not a bug.

Mike