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Techniques for Transmission Security via Fast Hopping in the Time-Frequency Grid

Techniques for Transmission Security via Fast Hopping in the Time-Frequency Grid. PI’s: Eli Yablanovich Rick Wesel Ingrid Verbauwhede Ming Wu Bahram Jalali. UCLA Electrical Engineering Department. What Kinds of Security Are Possible?. Security by Obscurity

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Techniques for Transmission Security via Fast Hopping in the Time-Frequency Grid

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  1. Techniques for Transmission Security via Fast Hopping in the Time-Frequency Grid PI’s: Eli Yablanovich Rick Wesel Ingrid Verbauwhede Ming Wu Bahram Jalali UCLA Electrical Engineering Department

  2. What Kinds of Security Are Possible? • Security by Obscurity • This is no security at all. Obscurity is fleeting. • Security by computational difficulty • Standardized systems like DES and AES rely on this. • Must consider attacks where plain-text is known. • The one-time pad that nobody else knows • Perfect as long as the pad remains secret.

  3. Physical Layer Security • Most sophisticated security techniques add security at the source only. • Our technique adds security at the physical layer. • Given that many messages in the network will already be encrypted, why should we do that?

  4. Why Have Physical Layer Security? • Increase the difficulty of attack, even with plaintext available. (The ciphertext of an individual stream is now difficult to receive.) • Enhances security. • Significantly enhances archival security.

  5. 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 The User-Message Grid User Diagonal Dappled Bricked Checked Symbol Time

  6. Time-Wavelength Grid (WDM) Wavelength 1 Wavelength 2 Wavelength 3 Wavelength 4 Time

  7. Periodic Wavelength Hopping • Each user appears on exactly one wavelength each symbol time. • Users cycle through wavelengths in a predictable fashion. 1 2 3 4 Wavelength 1 1 2 3 4 Wavelength 2 1 2 3 4 Wavelength 3 1 2 3 4 Wavelength 4 Time

  8. Random Wavelength Hopping • Each user appears on exactly one wavelength each symbol time. • Users select wavelengths in an unpredictable fashion. 1 2 3 4 Wavelength 1 1 2 3 4 Wavelength 2 1 2 3 4 Wavelength 3 1 2 3 4 Wavelength 4 Time

  9. Random Grid Hopping • A user appears on zero, one, or more wavelength each symbol. • Users select positions in grid in an unpredictable fashion. 1 2 1 4 Wavelength 1 2 2 3 1 Wavelength 2 1 4 3 2 Wavelength 3 4 3 3 4 Wavelength 4 Time

  10. Advantage of Random Hopping on the Grid • Even if an eavesdropper can tell which elements of the grid are being used by a transmitter, the eavesdropper still does know how to permute the bits to understand the data.

  11. 1 2 3 4 1616 Switch 1 2 1 4 1 2 3 4 2 2 3 1 1 2 3 4 1 4 3 2 1 2 3 4 4 3 3 4 Grid-to-Grid (G2G) Mapping

  12. 1 2 3 4 1616 Switch 1 2 1 4 1 2 3 4 2 2 3 1 1 2 3 4 1 4 3 2 1 2 3 4 4 3 3 4 Grid-to-Grid Mapping is a Switch • There are 16! possible configurations of this switch. • The switch configuration may be specified by log2(16!)=44.25 bits.

  13. Code bit = 0 Code bit = 1 A Pipelined Switch • There are 16! possible configurations (44.25 bits). • There are 56 bits used to specify the configuration. • Several bit patterns specify the same configuration.

  14. Security of Grid-to-Grid Mapping • This mapping needs to be cryptographically secure. • Pseudo-random sequences (Maximal-length sequences) are not secure. • A time-fixed mapping is not secure. • We’ll ultimately use DES/AES encryption technology to produce G2G mappings from “cryptographically-secure” random sequences. • Our first demo will use a linear feedback shift register for simplicity.

  15. 1 2 3 4 1 2 1 4 1 2 3 4 2 2 3 1 1 2 3 4 1 4 3 2 1 2 3 4 4 3 3 4 The Big Picture 56 bits (9 Gbits/sec) Advanced Encryption Standard Random bit generator (initially just a linear feedback shift register)

  16. Design # 1 # 2 # 3 # 4 # 5 Clock per Sample 1 1 4 5 4 Pipe stages per round 4 stages 4 stages 3 stages 4 stages 4 stages Total pipe stages 4  10 stages 4  10 stages 3  10 stages 4  10 stages 4  10 stages Latency 4  10 cycles 4  10 cycles 4  3  10 cycles 5  3  10 cycles (4  10) + 4 cycles FPGA Throughput (200MHz) 25.6 Gbit/s 25.6 Gbit/s 6.4 Gbit/s 6.4 Gbit/s 6.4 Gbit/s ASIC Critical path 1.5 ns 650 MHz 1 ns 1 GHz 1.5 ns 650 MHz 1 ns 1 GHz 1 ns 1 GHz Estimated Area Less than 500 Kgates Less than 900 Kgates Less than 150 Kgates Less than 300 Kgates Less than 250 Kgates ASIC Throughput (128*650) 83.2 Gbit/s (128*1) 128 Gbit/s (128*650/4) 20.8 Gbit/s (128*1/5) 25.6 Gbit/s (128*1/4) 32 Gbit/s Fast-enough AES implementation

  17. Pat. Gen Ping-Ponging Switches 155MHz 2.5Gbps 2.5Gbps 16X16 Switch 1:16 16:1 User 1 Modulator l1 16X16 Switch 1:16 16:1 User 2 Modulator l2 4:1 16X16 Switch 1:16 16:1 User 3 Modulator l3 16X16 Switch 1:16 16:1 User 4 Modulator l4 Serializer 1:16 16:1 de-Serializer

  18. Summary • The random mapping changes with every grid through a high-rate random sequence of bits (common to transmitter and receiver). • The two main non-optical implementation issues are • a fast switch (accomplished through pipelining and ping-ponging) • a fast AES implementation.

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