Re: homograph attacks

Martin Duerst wrote:
>  >I don't see how this is relevant for this discussion. If the .com
>  >registrar decides to use a subset of 639 only, I consider this a valid
>  >choice. No need to register any language tag with IANA; all tags
>  >you ever want to use are already there.
> 
> Not exactly correct. For cases like Serbian, Azerbaijani, Tajik,
> which can be written with different scripts, you need more than
> ISO 639.

Please read my statement again. *If* the registrar decides to use
a subset of 639 only, *then* all tags you ever want to use are
already there.

Now, the question is how the registrar deals with 639 languages
that use multiple scripts. There are two obvious options:
1. all characters in any of the scripts of the language can be
    allowed in a domain label (allowing for unintended homographic
    labels)
2. the characters of the language are separated into disjoint
    scripts, and each label registered for a language is required
    to fall into one script.

There are other options as well, of course: the registrar could
try to block labels in other scripts than the registered one,
if they are transliterations of each other. For example, for
Tajik, it might be sensible to block a Latin label if the
equivalent Cyrillic one has been registered.

Regards,
Martin