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On-Board Encryption in Satellites

On-Board Encryption in Satellites. Tanya Vladimirova, Roohi Banu and Martin N. Sweeting. VLSI Design and Embedded Systems Research Group Surrey Space Centre School of Electronics and Physical Sciences University of Surrey Guildford, UK, GU2 7XH. Presentation Overview.

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On-Board Encryption in Satellites

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  1. On-Board Encryption in Satellites Tanya Vladimirova, Roohi Banu and Martin N. Sweeting VLSI Design and Embedded Systems Research Group Surrey Space Centre School of Electronics and Physical Sciences University of Surrey Guildford, UK, GU2 7XH MAPLD 2005/184

  2. Presentation Overview • The Need for On-Board Security Services • Security Services in EO Satellites • Existing Security Services in Satellites • Required Security Services in Satellites • Proposed On-Board Security Architecture for Small Satellites • The Advanced Encryption Standard (AES) • Algorithm and Hardware Implementations • Fault Detection and Correction Model for On-Board Use • Simulation Results • Conclusions MAPLD 2005/184

  3. The Need for On-Board Security Services • Intrusions into Satellite Data • A team at the Embry Riddle Aeronautical University managed to obtain NOAA satellite imagery with the basic apparatus built as a part of their experimental project by using open Internet sources • Recently, researchers from a Japanese University were able to access data from the NASA’s Earth observation satellite LandSat as it flew over Japan • Future Space Internet • The NASA’s vision of “Space Internet” envisages that satellite users and scientists can directly access the satellite just like any other computer over Internet to get the required information • Allowing direct access to spacecraft certainly gives lots of flexibility, but at the cost of threats such as unauthorized access and illegal use of valuable data. • Eventually the problems faced by Internet due to inadequate security measurements will be repeated with the Space Internet. MAPLD 2005/184

  4. Security Services • Confidentiality (Encryption)- a service used to keep the contents of information accessible to only those authorized to access it. • Integrity- a service used to make sure that data is not modified, deleted or inserted with some other data by unauthorized users. • Authentication is a service that is concerned with assuring that origin of a message is correctly identified. MAPLD 2005/184

  5. Spacecraft Algorithms Used Implementation What is Name Platform Encrypted? STRV 1d Data Encryption Standard Software on Low-rate downlink (DES) SPARC processor METOP ExOR Hardware High-rate downlink KOMPSAT - II International Data Hardware High-rate downlink Encryption Algorithm (IDEA) (EPS) Triple Data Encryption Hardware High-rate downlink EUMETSAT’s Standard (3 - DES) polar System Existing Security Services in EO Satellites MAPLD 2005/184

  6. Existing Security Services in EO Satellites - Summary • Only the downlink is protected by encryption • Existing satellites use old or proprietary algorithms for downlink encryption • The other security services, like authentication and data integrity services, required for protection of the communication links are not addressed MAPLD 2005/184

  7. Required Security Services in Satellites • Uplink : • should be checked for integrity and authentication in order to protect the satellite from being taken over by unauthorized personnel. The issue of Uplink protection was highlighted in the US General Accounting Office report (GAO-02-781). • Downlink : • should be encrypted with secure and suitable algorithms to protect the valuable and sensitive data transmitted to ground. MAPLD 2005/184

  8. SSTL Small Satellite Platforms MAPLD 2005/184

  9. The Disaster Monitoring Constellation (DMC) Program • The DMC program is a novel international partnership, comprising a network of five low cost small satellites and ground stations. • The satellites are designed and manufactured by SSTL as a Know-How transfer to the participating countries: the United Kingdom, Nigeria, Algeria, Turkey and China. • From a low Earth orbit (LEO), each satellite provides 32 metre multispectral imaging (green, red, infrared), over a 600 km swath width. • The DMC program offers the possibility for daily revisiting of any point on the globe. AlSat-1 MAPLD 2005/184

  10. DMC Images • UK-DMC image of England (32m) MAPLD 2005/184

  11. Proposed Security Architecture MAPLD 2005/184

  12. On-Board Data Processing - Constraints • Small Satellites are resource constrained in terms of – power, computational resources, etc • A typical small satellite has the following parameters: • Algorithms used on-board satellites • should consume low power and computational resources and yet • deliver the throughput demanded by the satellite high-speed downlink MAPLD 2005/184

  13. Encryption Algorithms for On-Board Use The algorithms used on-board should be suitable to be implemented in a resource-constrained environment. MAPLD 2005/184

  14. Advanced Encryption Algorithm (AES) • Originally known as Rijndael after its Belgium creators Daemen-Rijmen • Endorsed as AES by the US National Institute of Standards and Technology (NIST) in 2002 • Suitable for a wide variety of platforms - ranging from smart cards to servers • Much simpler, faster and more secure MAPLD 2005/184

  15. The AES Algorithm • AES is an iterative algorithm • Each iteration is known as ROUND • The number of rounds depends on key and data block size • Each round consist of four transformations: • SubBytes • ShiftRows • MixColumns • AddRoundKey MAPLD 2005/184

  16. AES Transformations • TheSubBytesround transformation: • Two steps:Galois Field multiplicative inverse of each byte followed by affine transforms • Implementation approaches : • Look-Up Table (LUT) approach - a predefined 256 X 8 LUT is used • Non-LUT approach - Extended Euclid, Composite Field Arithmetic, Powers of Primitive Elements (Generators), Itoh Tsujii’s Algorithm MAPLD 2005/184

  17. AES Transformations (Cont.) • ShiftRows is carried out by a left shift operation • MixColumns: • Uses Galois Field multiplication with a predefined vector [2 3 1 1] • Implementation approaches: • LUT approach - Predefined Log, Antilog tables • Non-LUT approach - Galois Field multiplication • AddRoundKeyis an EXOR operation between data and key blocks MAPLD 2005/184

  18. AES Hardware Implementation Survey MAPLD 2005/184

  19. AES Verilog IP Core (source: www.opencores.org) SubBytes – S-Box Look-Up Table (256 bytes of S-Box are stored in memory ) MixColumn – Galois field multiplication over field GF(2) (involves a single bit left shift followed by addition) The round permutation module performs 10 iterations (for 128 bit keys). MAPLD 2005/184

  20. AES IP Core - Performance Experimental results: • FPGA - XC2V1000 • The encryption takes 13 clock cycles to encrypt a 128-bit data block • The frequency is 25 MHz. (Back annotated simulation frequency) Throughput = (128/13)*25*106 = 246 Mbps CAD tools: • Pre & post synthesis and back annotated simulations - ModelSim • Synthesis - Synplify • Implementation - Xilinx ISE MAPLD 2005/184

  21. AES for Satellites: Radiation Issues • Satellites operate in harsh radiation environment • The implementation should be robust to radiation induced bit flip errors • On average 64 bits (50 %) are corrupted with a single error during encryption using AES !!! • The bit flip errors must be detected and corrected in order to avoid the transmission and use of corrupted data MAPLD 2005/184

  22. Existing AES Fault Detection Models • The available AES fault detection models are classified into two categories: • Redundancy Based • A decryption module is used in parallel with the encryption module and its output is compared with the input to the encryption module to detect a fault. • More hardware overhead • Parity Based • The fault is detected by comparing the predicted parity with the calculated parity at the end of each transformation • Less hardware overhead • There are no fault-tolerant correction models for the AES algorithm MAPLD 2005/184

  23. Parity-Based Fault Detection Model for AES • The fault detection model is based on parity prediction • Parity is pre-calculated and stored in the parity memory • Given the input state, parity is predicted from the parity memory and compared with the calculated parity at the end of each round • Parity mismatch will lead to fault detection MAPLD 2005/184

  24. Proposed Fault Correction Model for AES • The fault correction model is based on the Hamming code (12,8) • The Hamming code is pre-calculated and stored in the Hamming code parity memory • Given the input state, the Hamming code is predicted from the parity memory and compared with the calculated Hamming code at the end of each round • A Hamming code mismatch will lead to a fault detection and to a subsequent single-bit fault correction. MAPLD 2005/184

  25. AES Fault Detection & Correction JAVA Software Simulation • JAVA software was developed to simulate the AES fault detection and correction scheme • GUI was also developed to effectively display the fault injection and correction: • input sub-frame - displays the input data block, encryption key, cipher block and decipher block etc • inject error sub-frame - is used to simulate the error injection at different levels: round, transformation, byte and bit position • details sub-frame, which shows: • the intermediate state of the output for every transformation and for every round in AES and • the predicted and calculated parity or the Hamming code. MAPLD 2005/184

  26. AES Fault Detection Model Software Simulation in JAVA MAPLD 2005/184

  27. AES Fault Correction Model Software Simulation in JAVA MAPLD 2005/184

  28. Conclusions • Security services required for overall satellite protection has been identified and an on-board security architecture has been proposed. • The AES has been identified as a suitable encryption algorithm for on-board use in small satellites. • An AES fault detection model based on parity prediction has been developed and verified by software simulation. • A novel AES fault correction model to prevent single bit faults occurring due to radiation (SEUs) has been proposed, developed and verified. • The proposed AES fault detection and correction model can also be used in other harsh radiation environments, for example in unmanned aerial vehicles, etc. MAPLD 2005/184

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