The OID is used to hold an identifier for the data types and data structures that comprise the fields of a certificate or CRL. The underlying representation and meaning of the identifier is defined by the CL module. For example, a CL module can choose to represent its identifiers in any of the following forms:

• A character string in a character set native to the platform.
• A DER-encoded X.509 OID that must be parsed.
• An S-expression that must be evaluated.
• An enumerated value that is defined in header files supplied by the CL module.

typedef CSSM_DATA CSSM_OID, *CSSM_OID_PTR;