encoding an X.509 certificate

["Tom Scavo" <trscavo@xxxxxxxxx>]

I've asked the following question in a number of forums with no luck.
I'm hoping someone with intimate knowledge of ASN.1 encodings can help
me out here.  Many thanks in advance.

Currently there are three profiles before the OASIS Security Services
Technical Committee (SSTC) that rely on XML elements of the form:

<ds:KeyInfo xmlns:ds="http://www.w3.org/2000/09/xmldsig#";>
 <ds:X509Data>
   <ds:X509Certificate>
MII...
   </ds:X509Certificate>
 </ds:X509Data>
</ds:KeyInfo>

Interestingly, the above element has sparked a vigorous debate within
the SSTC, which has since spread to the W3C XML Signature WG.  The
issue involves the ASN.1 encoding of the underlying certificate (which
is base64 encoded in the XML).  Specifically, should the certificate
be DER-encoded or should the encoding be left unspecified?

So my question is:  If you were given an X.509 certificate of unknown
encoding, could you determine the encoding by simply inspecting the
bytes?  Does your favorite ASN.1 library support such a function?

Thanks for shedding some light on this issue.

Tom Scavo
NCSA