Re: [dnsext] Adopting draft: draft-hoffman-dnssec-ecdsa-04.txt

[Chris Thompson <[e-mail]>]

On Jan 5 2011, Edward Lewis wrote:

>I'd like to see this stated in DNS terms - i.e., the notion of 
>strength is not one of them.
>
>I would suggest that
>
>  - the authoritative set of the DS record SHOULD include a DS RR for 
>each key that is of the same hash algorithm as is used in the key and 
>MAY have other hashes (and MAY even have only other hashes[1])
>
>[1] The parenthetical comment is redundant, put it there for emphasis.
>
>  - a validator SHOULD prefer the DS record of the same hash algorithm 
>over other hash algorithms for a key. 

You mean that a validator should prefer a digest type 1 (SHA-1) DS over
a type 2 (SHA-256) DS if the key to be validated uses algorithm RSASHA1?
This directly contradicts the SHOULD in RFC 4509 section 3, and also
doesn't seem too sensible to me.

>                                       Prefer means that it SHOULD be 
>the first tried and if it fails, the validator MAY declare failure 
>without examining the other applicable hash algorithms.  A validator 
>MUST NOT require that there be a hash of the same algorithm present, 
>with require meaning - if such a hash is absent, failure is not 
>automatic.
>
>You may note that I spec "the same hash algorithm" because I don't 
>know of any way to say if one hash algorithm is stronger than the 
>next.  I.e., bit length might be an indicator but I bet it also isn't 
>reliable.

It's perfectly possible for an implementor, or an operator, to have
opinions about this, though.

-- 
Chris Thompson               University of Cambridge Computing Service,
Email: [e-mail]    New Museums Site, Cambridge CB2 3QH,
Phone: [phone]       United Kingdom.