The SUBJECTID2 element contains the certificate subject identifier of the component that is communicating with another component, which is in turn communicating with the Digital Rights Management client component. This element is used only if SUBJECTID1 is the subject identifier of an SDK. The subject identifier is taken from the certificates that are used to establish secure channels between components. It uniquely identifies a component. For example, the version of an application or an SDK can be a subject identifier.
The SUBJECTID2 element MUST be present, even if empty.