  We present three quantum key distribution protocols using entangled state. In
the first two protocols, all Einstein-Podolsky-Rosen pairs are used to
distribute a secret key except those chosen for eavesdropping check, because
the communication parties measure each of their particles in an invariable
measuring basis. The first protocol is based on the ideal of qubit transmission
in blocks. Although it need quantum memory, its theoretic efficiency
approximates to 100%. The second protocol does not need quantum memory and its
efficiency for qubits can achieve 100%. In the third protocol, we present a
controlled quantum key distribution using three-particle entangled state to
solve a special cryptographic task. Only with the controller's permission could
the communication parties establish their sharing key and the sharing key is
secret to the controller. We also analyze the security and the efficiency of
the present protocols.
