Re: Difference between ASN_OPAQUE and ASN_OCTET_STR? (except for the display)

>>>>> "DS" == Dirk Süsserott <[email protected]> writes:

DS> The question is: Does this also apply to the type ASN_OPAQUE, i.e. can I 
DS> safely interchange the types ASN_OCTET_STR and ASN_OPAQUE?
DS> Do they have the very same behaviour regarding memory handling and 
DS> differ only in the type? That would be great for my purpose.

Generally, you should never use OPAQUEs.  If you have an application
specific binary blob of data, you should put it in an OCTET STRING.

An OPAQUE is a special type that was actually deprecated in SMIv2, so
it's not even supposed to be used.  The goal of it was to allow for
extensibility but the SMI authors dropped it from suggested usage in
second version of the language.

OPAQUEs must also be a double wrapped BER sequence.  IE, normally an
octet string when encoded looks like 0x04 LEN .. .. ..; An opaque, on
the other hand, needs to enclose another BER wrapped type internally.
Thus, the first byte encoded in the value beyond the length field MUST
be another BER type code, followed by a length.
-- 
Wes Hardaker
Sparta, Inc.

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