Re: [secdir] secdir review of draft-ietf-csi-send-name-type-registry-03

[Stephen Kent <[e-mail]>]

At 6:38 PM +0200 5/8/10, Roque Gagliano wrote:
>Patrick,
>
>Thank you for your review.
>
>You are correct oonly 160 bits SHA-1 hash is defined in RFC 5280 and 
>required in draft-ietf-sidr-res-cert
>
>Regards,
>
>Roque

Roque,

5280 defines how to use SHA-1, but it does not require use of this specific
hash function. 4.2.1.2 says:

    For CA certificates, subject key identifiers SHOULD be derived 
from the public key or a method that generates unique values.  Two 
common methods for generating key identifiers from the public key are:

...

Other methods of generating unique numbers are also acceptable.

So, use of another one-way hash function, e.g., SHA-256 meets the 
criteria defined above (associated with the "SHOULD") and is 
consistent with the final comment.

CAs need to know which function to use, but RPs just perform 
comparisons. We could modify the RPKI cert profile (if Geoff and the 
SIDR WG don't mind) to specify use of SHA-256 for generation of 
SKI/AKI values. I guess the real issue is whether commonly used 
software (e.g., OpenSSL) will support this.

Steve