[Standards] XEP-0115 redux

[Justin Karneges]

On Thursday 10 January 2008 8:32 am, Peter Saint-Andre wrote:
> The hashing algorithm matters because when you send me caps, I need to
> verify the contents (i.e., the long string of identity+features that you
> used as input to the hash function). The spec says:
>
>     The requesting entity MUST check the identities and supported
>     features against the 'ver' value by calculating the hash as described
>     under Generation of the ver Attribute and making sure that the values
>     match.
>
> This helps me be sure that you're not poisoning the caps ecosystem. But
> if you used SHA-384 to generate the hash and I don't support that
> algorithm, then I can't verify the contents.
>
> Or so it seems to me. :)

In the case where you don't understand the hash algorithm, would it be enough 
to simply cache the hash value on a per-jid basis and not bother verifying 
it?  As I understand it, the only reason for the security discussion we're 
having is because one jid is allowed to speak for another.  However, per-jid 
caching is naturally secure and should be quite effective if your client has 
a disk cache.

-Justin