[Cryptography] [FORGED] Re: Is ASN.1 still the thing?

Nico Williams nico at cryptonector.com
Wed Nov 15 16:03:57 EST 2017

On Wed, Nov 15, 2017 at 09:52:13PM +0100, Erwann ABALEA wrote:
> 2017-11-15 18:10 GMT+01:00 Nico Williams <nico at cryptonector.com>:
> > Mind you, just using BER/DER/CER is not sufficient, since a decoder is
> > free to produce an error when it sees unexpected SEQUENCE fields.  And
> > for CHOICEs and SETs the extensibility markers are even more important.
> A decoder doing that wouldn't be compliant. X.690 Clause forbids it.
> [...]
> The clause is present (without the NOTE) in the 1997 edition of the
> standard.

Right, but IIRC it was not in the 1984 version, or there were such
implementations back then.  And in any case, non-TLV encodings like PER
require knowledge of extensibility markers, thus they were added.

IIRC ASN.1's creators never expected to add something like PER, but they
did it because of complaints from the IETF crowd about the silliness of
TLV encodings, about the superiority of "bits on the wire" specs to TLV.

The IETF participants who complained were right, and the ITU-T was right
to respond by adding PER.  (Which goes to show that the ASN.1 community
was and probably still is responsive.)

(I wasn't there.  This is memory of reading about this history.)


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