A key management protocol (such as Key Management Interoperability Protocol (KMIP)) is extended via set of one or more custom attributes to provide a mechanism by which clients pass additional metadata to facilitate enhanced key provisioning operations by a key management server. The protocol comprises objects, operations, and attributes. Objects are the cryptographic material (e.g., symmetric keys, asymmetric keys, digital certificates and so on) upon which operations are performed. Operations are the actions taken with respect to the objects, such as getting an object from a key management server, modifying attributes of an object and the like. Attributes are the properties of the object, such as the kind of object it is, the unique identifier for the object, and the like. According to this disclosure, a first custom server attribute has a value that specifies a keygroup name that can be used by the key management server to locate (e.g., during a Locate operation) key material associated with a named keygroup. A second custom server attribute has a value that specifies a keygroup name into which key material should be registered (e.g., during a Register operation) by the server. A third custom server attribute has a value that specifies a default keygroup that the server should use for the device passing a request that include the attribute. Using these one or more custom server attributes, the client taps into and consumes/contributes to the key management server's provisioning machinery.