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Optical Transmission Security with Fast Frequency Hopping Code Division Multiple Access

Optical Transmission Security with Fast Frequency Hopping Code Division Multiple Access. Eli Yablanovich Rick Wesel Ming Wu Bahram Jalali. UCLA Electrical Engineering Department. What Kinds of Security Are Possible?. Security by Obscurity This is no security at all. Obscurity is fleeting.

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Optical Transmission Security with Fast Frequency Hopping Code Division Multiple Access

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  1. Optical Transmission Security with Fast Frequency Hopping Code Division Multiple Access Eli Yablanovich Rick Wesel 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 Green User 1 2 3 4 Blue User 1 2 3 4 Magenta User 1 2 3 4 Brown User The User-Message Grid Time

  6. Time-Wavelength Grid (WDM) 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

  7. Periodic Wavelength Hopping 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 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 1 2 4 1 Wavelength 1 2 2 3 2 Wavelength 2 4 3 3 4 Wavelength 3 1 4 3 1 Wavelength 4 Time

  10. Advantage of Random Grid Hopping • 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. Grid-to-Grid (G2G) Mapping • Need to map User-Message Grid to Wavelength-Time Grid. • 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 use DES/AES encryption technology to produce G2G mappings from “cryptographically-secure” random sequences.

  12. From Random Sequence to Indices • The random sequence is used to assign slot to each element of the time-frequency grid. • Because the random sequence can repeat values, each random number is an offset into the unassigned elements. • Each user knows which slots in which it should transmit. This set of slots may be viewed as a channel.

  13. Example • Generate 16 random numbers between 1 and 16. • 7, 15, 5, 8, 3, 9, 16, 13, 16, 3, 11, 2, 6, 12, 4, 1

  14. 7, 15, 15, 8, 3, 9, 16, 13, 1, 3, 11, 2, 6, 12, 4, 1 Wavelength 1 Slot-1 Wavelength 2 Wavelength 3 Wavelength 4 Time

  15. 7, 15, 15, 8, 3, 9, 16, 13, 1, 3, 11, 2, 6, 12, 4, 1 Wavelength 1 Slot-1 Wavelength 2 Wavelength 3 Slot-2 Wavelength 4 The fifteenth available slot Time

  16. 7, 15, 15, 8, 3, 9, 16, 13, 1, 3, 11, 2, 6, 12, 4, 1 Wrap around when you get to the end Slot-3 Wavelength 1 Slot-1 Wavelength 2 Wavelength 3 Slot-2 Wavelength 4 Time

  17. 7, 15, 15, 8, 3, 9, 16, 13, 1, 3, 11, 2, 6, 12, 4, 1 Slot-3 Slot-9 Slot-16 Slot-5 Wavelength 1 Slot-12 Slot-8 Slot-1 Slot-10 Wavelength 2 Slot-7 Slot-4 Slot-13 Slot-15 Wavelength 3 Slot-6 Slot-11 Slot-14 Slot-2 Wavelength 4 Time

  18. Assign Green User to Slots 1, 5, 9, 13 Slot-3 3 Slot-16 2 Wavelength 1 Slot-12 Slot-8 1 Slot-10 Wavelength 2 Slot-7 Slot-4 4 Slot-15 Wavelength 3 Slot-6 Slot-11 Slot-14 Slot-2 Wavelength 4 Time

  19. Assign Blue User to Slots 2, 6, 10, 14 Slot-3 3 Slot-16 2 Wavelength 1 Slot-12 Slot-8 1 3 Wavelength 2 Slot-7 Slot-4 4 Slot-15 Wavelength 3 2 Slot-11 4 1 Wavelength 4 Time

  20. Assign Magenta User to Slots 3, 7, 11, 15 1 3 Slot-16 2 Wavelength 1 Slot-12 Slot-8 1 3 Wavelength 2 2 Slot-4 4 4 Wavelength 3 2 3 4 1 Wavelength 4 Time

  21. Assign Brown User to Slots 4, 8, 12, 16 1 3 4 2 Wavelength 1 3 2 1 3 Wavelength 2 2 1 4 4 Wavelength 3 2 3 4 1 Wavelength 4 Time

  22. Some slots can be stuffed with junk.Lets put junk in everyone’s third slot. 1 3 4 2 Wavelength 1 3 2 1 3 Wavelength 2 2 1 4 4 Wavelength 3 2 3 4 1 Wavelength 4 Time

  23. Some slots can be stuffed with junk.Lets put junk in everyone’s third slot. 1 3 4 2 Wavelength 1 3 2 1 3 Wavelength 2 2 1 4 4 Wavelength 3 2 3 4 1 Wavelength 4 Time

  24. Summary • The random mapping changes with every grid through a cryptographically secure random sequence. • AES/DES random sequence generator uses a seed that is refreshed occasionally using public-key cryptography. • Eavesdropper doesn’t know • Where a user is transmitting • How to properly reverse permutation • Which bits are junk. • Overall, this provides real security by itself and greatly increases difficulty of decrypting or even archiving.

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