Lecture 15: ASN.1 and BER Intro

Object Identifiers

ASN.1 might be of only passing interest were it not for the OBJECT IDENTIFIER^[4] data type. An

OBJECT
IDENTIFIER

is a simple ASN.1 data type with special properties.

An OBJECT IDENTIFIER is a data type denoting an authoritatively named object, regardless of the type of the object which it names.

It is written as a sequence of non-negative integer values which describe a traversal of a tree. The tree consists of a root connected to a number of labelled nodes via edges.

Each label consists of a non-negative integer value and an optional brief textual description (or

Object
Descriptor

). The most common format for writing down the value of an OBJECT IDENTIFIER is as a dotted sequence, thus:

1.0.8571.5.1

This identifies the object found by starting at the root, moving to the node with label 1, then moving to the node with label 0, and so on. The node found after traversing this list is the one being identified.

^[4] and the related Object Descriptor type.

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