Re: [idn] Re: Legacy charset conversion in draft-ietf-idn-idna-08.txt

["James Seng" <jseng@pobox.org.sg>]

> Does the CD include more than what is available on the net from
> www.unicode.org/Public/MAPPINGS/?

Yes and No. I know there are very well documented mappings between ISO 10646
and national standards encoding in CDROM. There are some mappings which is
on Unicode website which is not in the CDROM.

> I can't find offical mappings for, e.g., ISO-2022 (RFC 1468) online.
>
> > - IDNA already specify (or suggested) that if the apps is using legacy
> > encodings, it should transcode to Unicode first.
>
> Yes, but I cannot find where it says how to do it, or where it cites a
> reference that explains how to do it.  That's why I think the security
> consideration should be more clear that the standard will enable
> trivial attacks that have security consequences if the document is
> implemented, because the details of legacy transcoding is left
> unspecified.

No. ISO-2022 specify a mechanism for encoding reportairs using code
switching. The transcoding varies depending on the reportairs (up to 4) you
select. And it is not a 1-to-1 mapping with Unicode.

Do you mean you want IDNA to specify transcoding algoirthm too? Then how
many do you want to support? And why only these set? What if some one
creates another encoding?

IDNA already say we start from Unicode. How you do the trancoding from your
encoding to Unicode is up to you so long you have the right Unicode to start
with, ie, the original legacy encoding is irrelevant from IDN perspective.

If you did not do your transcoding from legacy to Unicode, then there is a
security problem. But the beast you describe is not IDNA. IDNA specifically
say it operates from/to Unicode only.

> If there is no standard way to translate ISO-2022-JP into Unicode,
> won't different applications implement it differently?

There are many ways to implement an algorithm. It does not matter how you do
it, so long the end results is the same.

> Many machines use legacy encodings, how IDNA ends up being implemented
> on such systems seems to be up to the implementor right now.

Yes and yes. And Toolkits are available for implementors to transcode, MS
APIs, ICU, Java I18N API etc. Lets leave the implementation issues to the
implementors.

-James Seng