"On-Board Encryption in Satellites"
Tanya Vladimirova, Roohi Banu, and Martin Sweeting
Surrey Space Centre, University of Surrey
The unfortunate events of September 11th 2001 have raised awareness of the security threats posed by the unauthorized use of public assets. Satellites and the data that they generate are no exception. Although there are many encryption products and algorithms, the use of these products and algorithms on-board satellites and satellite networks has been over looked until recently. This is partly due to the impression that satellites are very complex and very far to the intruders to access its sensitive data. But this is no longer true, especially after the cases where it has been proved that intrusion into satellite data is not an impossible task [1,2]. The demand to protect the sensitive and valuable data transmitted from satellites to ground is increasing day by day and hence the need to use encryption on-board.
At present, very few satellites are using on-board encryption to protect the data transmitted to the ground station. The encryption algorithms used in present satellite missions are typically proprietary algorithms or outdated algorithms like DES  rather than using the latest encryption standards. The Rijndael algorithm approved as the Advanced Encryption Standard (AES) by the US National Institute of Standards and Technology (NIST) in October 2000 is being adopted by many organizations across the world. It is used across a wide range of platforms ranging from smart cards to big servers because of its simplicity, flexibility, easiness of implementation and high throughput. Therefore, the AES is well suited for resource constraint platforms like on-board satellites. The Consultative Committee for Space Data Systems (CCSDS) is considering recommending AES as the standard encryption algorithm for use on satellites .
This paper addresses the need for on-board encryption in satellites and summarizes the encryption schemes used in present satellites. It will discuss reliability issues related to direct use of commercial security algorithms like AES in satellites. In addition the challenges to optimal implementation of the AES using the available limited on-board resources in terms of power, area and speed will be outlined. The results of experimental work on reliable software and FPGA-based implementations of the AES algorithm targeting the resource constrained small satellite platform will be presented and compared.
Dr K. Sweet, “The Increasing Threat to Satellite Communications” Online Journal of Space Communication, Issue 6, November 2003.
US GAO Report, GAO-02-781, August 2002.
H.Weiss, J. Stanier, “Space Mission Communications Security, GSAW 2001.
“The application of CCSDS protocols to secure systems”. CCSDS 350.0.G-1. Green Book. March 1999.
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