CDMA port-to-port encryption communication system and key distribution method thereof

The invention discloses a CDMA port-to-port encryption communication system and a key distribution method thereof, the CDMA port-to-port encryption communication system comprises a CDMA network and a terminal mobile telephone thereof, a public switched telephone network and a terminal fixed-line telephone thereof, a short message service center as well as the following three cipher processing units including a cipher chip of a mobile telephone terminal, a key distribution management center (KDMC) and a Firmware cipher module of a gateway mobile switching center. The key distribution management center is used for key distribution management of the communication system. The key distribution is realized by a layered distribution method, i.e. a first layer is an equipment key which is distributed in the process of initialization; a second layer is a key-encryption key and a short message service key which are distributed in startup of an enciphered mobile telephone; and a third layer is a session key which is distributed every time a session is launched between the enciphered mobile telephones. At the same time, by adopting a bidirectional certification technology for key distribution and combination of a key update and remote destroying method, the safety risk in key exposure is reduced, and the communication safety is improved.