Object Identifier

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In computer science , an Object Identifier ( OID ) is a globally unique identifier that is used to name an information object (see URN ). An OID represents a node in a hierarchically assigned namespace that is defined by the ASN.1 standard. Each node is uniquely identified by a sequence of numbers that indicate its position starting at the root of the tree. New nodes for your own use can be requested from the relevant authorities of the superordinate node. The rules for the allocation and registration of OIDs are specified in the standards ITU-T Rec. ITU-T X.660, ISO / IEC 9834 and DIN 66334. The management of the OID tree and ensuring the uniqueness of OIDs are based on the Transfer of responsibility for the subordinate nodes to the owner ( Registration Authority ) of an OID.

notation

In the international OID tree, all edges from a node to child nodes are uniquely identified by whole numbers, so-called primary integer values . Different edges starting from the same node receive different primary integer values.

Each edge is equally with a unique Unicode designation (Unicode label) provided. In addition, an edge can have one or more secondary identifiers . The character restrictions for ASN.1 designations apply to the secondary designations (letters, digits and hyphen are permitted; see Recommendation ITU-T X.680 | ISO / IEC 8824-1). The secondary names do not have to be unique.

Each object is assigned to exactly one node (usually one leaf of the tree). For such an object, the ASN.1 Object Identifier is defined in the narrow sense as a sequence of the edge numbers on the path from the root to the corresponding node, e.g. B .:

{1 3 6 1 4 1} gemäß ASN.1-Notation (in diesem Beispiel ohne NameForm-Bezeichner),
1.3.6.1.4.1 gemäß Punkt-Notation,
urn:oid:1.3.6.1.4.1 gemäß URN-Notation,
/1/4/6/1/4/1 gemäß OID-IRI-Notation (in diesem Beispiel ohne NonInteger-Unicode-Label)

To improve readability, the value of an ASN.1 OID can be referenced using the associated secondary designations:

{iso(1) identified-organisation(3) dod(6) internet(1) private(4) enterprise(1)} gemäß ASN.1-Notation

The ASN.1 OID-IRI (OID internationalized resource identifier) ​​is created by concatenating the Unicode designation separated by a slash ('/'):

"/ISO/Identified-Organization/6/1/4/1" gemäß OID-IRI-Notation

Additional defined edges referenced by Unicode designations, so-called long arcs , can result in a shorter equivalent notation for the OID-IRI (similar to symbolic links in file systems).

root

The edges from the root of the OID tree were defined as follows:

0: ITU-T
1: ISO
2: joint-iso-itu-t

An extension by a further standardization organization is not technically possible because the binary coding of OIDs such as B. the BER / CER / DER coding in favor of compression no further space was reserved.

Application examples

  • OIDs are used in information security, for example, to clearly identify the object types in X.509 certificates.
  • In X.500 directory services , unique attributes, attribute types and objects are identified.
  • In LDAP schemas, all object classes and attribute types have their own OID.
  • In network technology, OIDs are used in connection with SNMP when an object from the Management Information Base is meant.
  • OIDs are also a central component of the HL7 and are used for the exchange of data between organizations in the healthcare sector and their computer systems.

Acquiring an OID

There are many ways to get an OID assigned, both paid and free. Some examples:

  • Free registrations are possible with IANA , the node (prefix) is 1.3.6.1.4.1 with the ASN.1 notation {iso (1) identified-organization (3) dod (6) internet (1) private (4) enterprise ( 1)} .
  • A UUID can be used as an OID component under node 2.25 ; no registration is required for this.
  • Objects for standardized data exchange in healthcare can be registered with DIMDI (for Germany), in the OID Portal Austria or with Refdata (for Switzerland) [1] .

See also

Web links

Individual evidence

  1. Recommendation X.680 ( English ) tu.int. Retrieved September 15, 2019.
  2. RFC 3061
  3. Recommendation ITU-T X.660 (07/11)
  4. Olivier Dubuisson: ASN.1 - Communication between heterogeneous systems , page 396 in the English version
  5. ITU-T X.690 (PDF; 524 kB) - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)