Re: [dnsext] MAR proposal #1: Algorithm downgrade protection

[Samuel Weiler <[e-mail]>]

On Fri, 1 Apr 2011, Samuel Weiler wrote:

> In order to provide some protection against algorithm 
> downgrade[1]...

I forgot to provide the footnote in my first message:

[1] Acknowledging that some algorithms may eventually become weak, but
such weaknesses may not be as clear and binary as "yesterday the
algorithm was secure and today it is totally broken", a zone signer
might wish to provide signatures from a more secure algorithm so that
newer validators can be protected while simultaneously providing older
(weak) signatures for the benefit of validators that have not been
upgraded.  Without a signaling mechanism such a this, a validator
supporting both old and new algorithms may find itself accepting
forged answers signed only with the old (and broken!) algorithm.

Alternatives to this mechanism include disabling the broken algorithm
in the validator (which could unnecessarily prevent validation of
zones that haven't signed with something stronger) or implementing a
preference system in the validator (e.g. "if the zone is signed with
WeakAlgA and StrongAlgB, ONLY check the signatures from StrongAlgB").