  We present a protocol for quantum cryptographic network consisting of a
quantum network center and many users, in which any pair of parties with
members chosen from the whole users on request can secure a quantum key
distribution by help of the center. The protocol is based on the quantum
authentication scheme given by Barnum et al. [Proc. 43rd IEEE Symp. FOCS'02, p.
449 (2002)]. We show that exploiting the quantum authentication scheme the
center can safely make two parties share nearly perfect entangled states used
in the quantum key distribution. This implies that the quantum cryptographic
network protocol is secure against all kinds of eavesdropping.
