  Quantum entanglement plays a pivotal role in many communication protocols,
like secret sharing and quantum cryptography. We consider a scenario where more
than two parties are involved in a protocol and share a multipartite entangled
state. In particular, we considered the protocol of Controlled Quantum Key
Distribution (CoQKD), introduced in the Ref. Chin. Phys. Lett. 20, 183-185
(2003), where, two parties, Alice and Bob establish a key with the cooperation
of other parties. Other parties control/supervise whether Alice and Bob can
establish the key, its security and key rate. We discuss the case of three
parties in detail and find suitable resource states. We discuss the controlling
power of the third party, Charlie. We also examine the usefulness of the new
resource states for generating conference key and for cooperative
teleportation. We find that recently introduced Bell inequalities can be useful
to establish the security of the conference key. We also generalize the
scenario to more than three parties.
