Subject: Re: Speak now or forever hold your peace...

From: Peter Sylvester <[email-masked]>
Date: Wed, 11 Aug 2004 17:55:56 +0200 (MEST)

> 
> > tags > 30 create most likely some problems in decoders, too.
> 
> You mean: In decoders badly hand-coded. ;)  I'm not aware of such a bug 
> with decoders generated by a compiler.

This is not a question of a bug, it is a question of whether
low level routines can supports tags > 30.

This has not much to do whether the syntax is treated by a compiler
but with the possibility of decoding larger value in low level routines
in a situation where all practical well known syntaxes do not have 
tags > 30, thus, the low level implementation of tag decoding can 
assume that you have only one octet for a tag.

I have not seen any compiler that is able to link againt a low level
decoder specific with the maximum tag length that can ever occur the
given compilation environment. 

how many compilers can handle a context tag of about 2**130

But well, we are somehow getting out of scope of this discussion.

---

From: Olivier Dubuisson <[email-masked]>
Date: Thu, 12 Aug 2004 17:03:38 +0200

> But well, we are somehow getting out of scope of this discussion.

We may be out of scope, but since your assertion about decoders looked 
wrong to me, I checked with Bancroft Scott from OSS Nokalva and here is 
what he said:
-----
There are **MANY** ASN.1 specs that have tags in excess of 30.
I know of no commercial-grade ASN.1 toolkit, nor any of the
popular free ones, that suffers from such a deficiency.

In the early 1990's the implementor's organization in Europe, the U.S.A
(NIST Stable Implementation Guideline) and Asia agreed that ASN.1 specs
should not use tag numbers greater than 16383, and implicitly, that tools
should support tags of at least that size.  To the best of my knowledge
all commercial-grade and popular free ASN.1 toolkits support tags this
large.
-----

Olivier