  We present a quantum secure direct communication protocol and a multiparty
quantum secret sharing protocol based on Einstein-Podolsky-Rosen pairs and
entanglement swapping. The present quantum secure direct communication protocol
makes use of the ideal of block transmission. We also point out that the sender
can encode his or her secret message without ensuring the security of the
quantum channel firstly. In the multiparty quantum secret sharing protocol, the
communication parties adopt checking mode or encoding mode with a certain
probability. It is not necessary for the protocol to perform local unitary
operation. In both the protocols, one party transmits only one photon for each
Einstein-Podolsky-Rosen pair to another party and the security for the
transmitting photons is ensured by selecting Z-basis or X-basis randomly to
measure the sampling photons.
