Re: DER coding of a default syntax value

Peter Williams <peter(_at_)verisign(_dot_)com> wrote:

> If I defined an X.509 v3 extension:
>
>  foo  EXTENSION ::= {
>        SYNTAX                  BOOLEAN : FALSE
>        IDENTIFIED BY           id-foo
>        }
>
> The DER-coding of a "false" boolean value for the extension
> would presumably not exist in the byte stream, under DER
> default coding rules.
>
> That is, the octet-string of the extension identified
> by id-foo would have no content octets, and thus be of
> length 0.
>
> Anyone disagree?

The definition of "foo" is invalid because what follows
"SYNTAX" must be a type, not a value.  So you need to drop the
": FALSE" to arrive at valid syntax.  Do you still think that
the DER-encoding does not exist in the byte stream?  My reading
is that it always will exist, but I am not 100% certain because
I am away from the office and don't have ready access to X.509v3.

Bancroft Scott
Open Systems Solutions, Inc.