Re: ASN.1 types for Distinguished names (was: Re: Distinguished names and

[Brian Korver <[e-mail]>]

Holger Reif writes:
> 
> Hi,
> 
> this seems to be a nice thread to jump in ;-)
> 
> I noticed that many of the X.520 Selected attributes are of type DirectoryString
> which in turn is a choice of teletexString, printableString and universalString.
> Does anybody know when which Form is to be used and wether a transformation 
> between these types (if possible) is allowed and gives equal meaning. 

BMPString has basically replaced UniversalString because, I have
been told, nobody used UniversalString.  I can be believe this.

Both TeletexString (T61String) and PrintableString have constraints as
to what can be placed in them.  So for instance if you need to use a
character such as '@', you cannot use PrintableString.

I'm unaware of any equality rules to use when comparing strings of 
unequal type.  I assume that most implementations assume that strings
of unequal type are by definition not equal.  IMHO this is the best
approach because of the lack of well-defined equality matching rules.

I'm also unaware of any rules for "which string do I use" when there
are multiple string types to choose from.


> Of course, if it's within a SIGNED context then the answer is clear: 
> one can't change the types. But in other cases?

brian
[e-mail]