[ietf-dkim] On per-user-keying

[Hallam-Baker, Phillip]

> From: John Levine [mailto:johnl at iecc.com] 

> Your hash and wildcard trick works great if the signatures 
> are all applied by an MTA under the control of the domain's 
> management.  But if you let roaming users sign their own mail 
> in the MUA, you really need to give each potentially 
> untrustworthy user a separate key.

Agreed, I think that is essential if you have MUA signing for a whole
heap of reasons. If I have a million users and a million copies of a
private key floating around then I have effectively lost control.

Basicially that would mean you end up with the cost and complxity of
running a public key scheme and get none of the benefit. You still have
to have a means of provisioning the key to the MUA.


If you are going to sign in the MUA you need a key lifecycle management
solution.