METEOSAT raw image data encryption

A stream cypher system is proposed for METEOSAT raw image data encryption. For each transmitted bit the stream cypher generates a key stream bit. This key steam bit is EXORED with the message bit before it is transmitted. The receiver does the same with the received encrypted cypher text bit and gets back the clear text message bit. Since the METEOSAT raw image transmission system already includes a sophisticated bit and line synchronization system, it is proposed that this be used also for cypher synchronization. Onboard and ground implementation, and key management, are described.