[Standards] XEP-0153: Encoding of photo hash?

Jonas Wielicki jonas at wielicki.name
Sat Feb 24 19:53:46 UTC 2018

Hi Christian,

On Samstag, 24. Februar 2018 20:22:39 CET Christian Schudt wrote:
> I’ve got a question about XEP-0153. Its XML schema defines that the photo
> hash is encoded as Base64:
> <xs:element name='photo' minOccurs='0' type='xs:base64Binary‘/>
> However, I’ve seen the hash encoded as hexadecimal, too. It was no small
> client, but it was Facebook. I don’t know how other clients behave.
> So I wonder, what is the correct encoding of the photo hash value: base64 or
> hex-encoded?

Now this is fun. First of all, the mantra: The Schemas Are Not Normative.

Second: I could’ve sworn that there was some text which specified something 
like lower-case hex. But apparently there is none. Grepping through the 
presence I get from all my contacts, all of them are doing lower case 
hexadecimal. When we implemented it in aioxmpp, we thus also went for lower 
case hexadecimal.

So I think we need to update the spec according to its current usage. 
Especially since we’re recommending to support it at least read-only.

Any objections to me adding a clarification in this regard?

kind regards,
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