Safety-alliance (SA) generation method for safety communication between nodes of network area

The invention includes following processing steps. One key administration center (KAC) is set up in the network area for each manager. The KAC is connected to each network nodes in the network area respectively. When one network node in the network area for the manager requests to make the secretive communication to one network node in the other network area of the another manager, the agent of the KAC in the two network areas negotiate about the security alliance (SA). The negotiated SA is distributed to the network nodes in respective network areas. The two network nodes in the network areas of the two managers utilize the SA received to carry out the secretive communication from end to end. The entity with monitoring function can be setup, obtaining the SA from the KAC so as to decryptand monitor the communication between the network nodes of the sending party and the target party.