[Standards] hash agility in file transfer

Dave Cridland dave at cridland.net
Wed Jun 15 19:35:24 UTC 2011


On Wed Jun  1 23:55:47 2011, Waqas Hussain wrote:
> But if we go with tags, do we even need to specify that? We can  
> always
> add tags later in new namespaces, even defined in new XEPs, e.g.
> <hash xmlns="new sha1 xmlns">...<hash>
> or
> <sha1 xmlns="new XEP-0096 namespace, or even the existing namespace,
> since the updated protocol is fully backwards compatible">...</sha1>

I dislike this, because it's harder for an app to say "Hey, this app  
sent me a hash function I don't understand", which can be interesting  
(perhaps not in FT, but in other cases).

Also, it requires more work than a textual name, since we have those  
defined and maintained for us at  
http://www.iana.org/assignments/hash-function-text-names

So therefore I'd like to suggest we consider an element: <hash  
xmlns='urn:xmpp:crypto:hash' function='sha-1'  
format='64|hex'>...</hash>

I appreciate this isn't as exciting and shiny as a new namespace and  
element name for every hash, but in effect, this has already defined  
8 hash functions, so we can move on and concern ourselves only with  
which one we want to recommend for now.

Dave.
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