[xri] Additional Requirement - Anonymization

Dear Drummond,

I'm very sorry for sending the additional requirement even though
F2F meeting is just around the corner.
If possible, it would be great if you could add the requirement
regarding anonymization.

I found though XNS spec. describes anonymization, there is 
no description regarding anonymization in the XRI requirements.

I believe that one of the great function of XNS is that it can technically 
protect XNS IDs so that the third person cannot resolve real XNS ID
of his/her counterpart. I don't want to lose this feature by any means,
and believe that any digital identity architecture should have these
kind of function. And thus I would like to remind it again just for the 
information.

Best regards,

Nomura Research Institute, T.Seki