Re: Coding of national characters?

["Anil R. Gangolli" <gangolli@xxxxxxxxxxxxxxxxxx>]

lars.gu.johansson@posten.se wrote:
> 
> We have a problem...
> 
> In PKIX part 1, chapter 4.1.2.4  "Issuer Name" the issuer field
> (and the subject field similarly) is defined. There are no
> mandatory X.520 attributes (like country or commonName etc)
> but the the DirectoryString is defined in ASN.1 as:
> 
> >  DirectoryString ::= CHOICE {
> >           teletexString           TeletexString (SIZE (1..maxSize)),
> >           printableString         PrintableString (SIZE
> (1..maxSize)),
> >           universalString         UniversalString (SIZE
> (1..maxSize))


I agree with Lars.

First, I believe the most current X.520 allows BMPString in this
choice.

Second, I believe we should just avoid encoding as TeletexString
(T61String)
altogether.

I'd like to see the precedence go:

- PrintableString  if it "fits"
- BMPString if it "fits"
- UniversalString

--a.

> 
> Below this definition it is stated that:
> 
> >   The directoryString is defined as a choice of PrintableString,
> >   TeletexString and UniversalString.  Conforming CAs shall choose
> from
> >   these options as follows:
> >
> >      (a) if the character set is sufficient, the string will be
> >      represented as a PrintableString;
> >
> >      (b) failing (a), if the teletexString charater set is
> sufficient,
> >      the string string will be represented as a TeletexString;
> >
> >      (c) failing (a) and (b), the string shall be represented as a
> >      UniversalString.
> 
> The problem for us outside the US is how to encode national
> characters.
> In Sweden for example, PrintableString which is equivalent to 7-bit
> ASCII
> is not sufficient. According to the standard we would then make use of
> teletexString which is equivalent to the T.61 character set.
> 
> Now, T.61 is an old standard that is very seldomly used nowadays. In
> particular neither Netscape Navigator nor Microsoft Internet Explorer
> make use of T.61.
> 
> Instead both Navigator and Explorer uses the character set in ISO
> 8859-1
> (Latin-1 which is equivalent to 8-bit ASCII). This character set is
> used for
> both the PrintableString tag and the teletexString tag.
> 
> Clearly the use of ISO 8859-1 in conjuction with the teletexString tag
> is an
> error and some X.500 directories won't accept this. The effect would
> be
> that searching these directories becomes impossible.
> 
> The other alternative (ISO 8859-1 with the PrintableString tag) looks
> very
> attractive IMHO and I would prefer that this solution were
> incorporated into
> the standard. There are still problems however: many complilers based
> on ASN.1 doesn't accept 8-bit characters in a PrintableString.
> 
> Can anyone on this list see a solution to this problem? If so, I would
> suggest
> that the PKIX-1 draft is updated accordinly.
> 
> Regards,
> /Lars Johansson
> Sweden Post

-- 
Anil R. Gangolli
Structured Arts Consulting Group
mailto:gangolli@StructuredArts.com
http://www.StructuredArts.com