KEY TRANSFORMS TO DISCRIMINATE BETWEEN BEAMS IN A MULTI-BEAM SATELLITE COMMUNICATION SYSTEM

摘要

A method and apparatus is described for transforming a key variable used for scrambling mobile data traffic between a terminal and a network in alternate ways based on a value transmitted to the terminal from the network. Transformation is accomplished by passing portions of the key variable through a series of S-boxes, which provide a mapping between inputs and outputs. The method and apparatus is explained also in the context of a satellite communications system, in which a terminal can be located in a different continent/country from the terminal's home location. Enciphered communication is enabled between the foreign satellite gateway and the roaming terminal after the foreign gateway communicates with the terminal's native gateway. The native gateway transmits one or more cipher variables in the communication. Moreover, the value determining which way to cipher the data traffic can be based on numerous factors, including aspects of the satellite communication system.