Re: [idn] comments on IDNA-04

["Adam M. Costello" <idn.amc+0@nicemice.net.RemoveThisWord>]

"Eric A. Hall" <ehall@ehsco.com> wrote:

> > I wanted a term for non-WYSIWYG label, that is, a label that doesn't
> > directly say what it means, and is therefore displayed differently
> > in IDNA-aware applications versus IDN-unaware applications.
> > Obviously, the definition "label that gets altered by ToUnicode"
> > corresponds exactly to this concept.
>
> Do you mean the IDN label that results from decoding, versus the STD13
> label with a prefix?

I mean X is an ACE label iff ToUnicode(X) != X.  This implies that for
any ACE label Y, nameprep(Y) is an all-ASCII string beginning with the
ACE prefix.  But not every all-ASCII string beginning with the ACE
prefix is an ACE label.

> I was/am under the impression that general purpose encoding and
> decoding libraries would exist to support the use of AMC-Z for non-DNS
> purposes

That may be true, but regardless of whether an application calls a
single ToUnicode function or calls smaller functions separately, if it
is IDNA-compliant it will either do nothing to the label or it will
perform ToUnicode or it will perform ToASCII, and all of those options
are safe from spoofing problems.

AMC