  We present a controlled secure direct communication protocol by using
Greenberger-Horne-Zeilinger (GHZ) entangled state via swapping quantum
entanglement and local unitary operations. Since messages transferred only by
using local operations and a public channel after entangled states are
successfully distributed, this protocol can protect the communication against a
destroying-travel-qubit-type attack. This scheme can also be generalized to a
multi-party control system.
