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Quantum Cryptography Mris Ozols University of Cambridge Overview - PowerPoint PPT Presentation

Quantum Cryptography Mris Ozols University of Cambridge Overview What are quantum computers? What is quantum cryptography? - Shor's algorithm for factoring - Quantum key distribution - Device-independent quantum cryptography What


  1. Quantum Cryptography Māris Ozols University of Cambridge

  2. Overview ● What are quantum computers? ● What is quantum cryptography? - Shor's algorithm for factoring - Quantum key distribution - Device-independent quantum cryptography

  3. What is quantum computing? Mathematics Quantum Computing Computer Physics Science

  4. Quantum mechanics

  5. How to simulate quantum physics? Simulating quantum systems on a regular computer is very hard... Wouldn't it be easier if the computer itself would operate based on the laws of quantum physics? Richard Feynman

  6. What is a quantum computer? + Quantum mechanics Computer Quantum computer is a device that processes information by using quantum phenomena

  7. What quantum computers are not...

  8. What quantum computers are not... just smaller

  9. What quantum computers are not... just smaller just faster

  10. What quantum computers are not... e x p o n e n t i a l l y just faster smaller just faster

  11. What quantum computers are not... e x p o n e n t i a l l y just faster smaller just science faster fiction

  12. What quantum computers are not... e x p o n e n t i a l l y just faster smaller just science faster fiction available for $ale

  13. Quantum cryptography ● Quantum algorithms for breaking existing cryptosystems - Shor's algorithm for factoring

  14. Quantum cryptography ● Quantum algorithms for breaking existing cryptosystems - Shor's algorithm for factoring ● Enabling secure communication - Quantum key distribution

  15. Quantum cryptography ● Quantum algorithms for breaking existing cryptosystems - Shor's algorithm for factoring ● Enabling secure communication - Quantum key distribution ● Computation with untrusted devices - Device-independent quantum cryptography

  16. Multiplying vs factoring Multiplying is easy... 3 × 5 = 15 11 × 13 = 143 28423087481 × 25162321141 = 715190855015658735821

  17. Multiplying vs factoring Multiplying is easy... 3 × 5 = 15 11 × 13 = 143 28423087481 × 25162321141 = 715190855015658735821

  18. Multiplying vs factoring Multiplying is easy... 3 × 5 = 15 11 × 13 = 143 28423087481 × 25162321141 = 715190855015658735821 Factoring is not... 12 = 3 × 4 377 = 13 × 29 57249035862524887649 = 2543563837 × 22507410677

  19. Multiplying vs factoring Multiplying is easy... 3 × 5 = 15 11 × 13 = 143 28423087481 × 25162321141 = 715190855015658735821 Factoring is not... 12 = 3 × 4 377 = 13 × 29 57249035862524887649 = 2543563837 × 22507410677

  20. Public-key cryptography (RSA)

  21. Public-key cryptography (RSA) Private key Public key 2543563837 57249035862524887649 22507410677

  22. Public-key cryptography (RSA) Private key Public key Message 2543563837 57249035862524887649 22507410677 Encrypt

  23. Public-key cryptography (RSA) Private key Public key Message 2543563837 57249035862524887649 22507410677 Encrypt Decrypt Message

  24. Shor's algorithm breaks RSA ● Produces prime factors of a given integer ● Runs in polynomial time (best known classical algorithm runs in exponential time) Peter Shor

  25. Shor's algorithm breaks RSA ● Produces prime factors of a given integer ● Runs in polynomial time (best known classical algorithm runs in exponential time) ● Based on quantum Fourier transform Peter Shor Fourier transform of Peter Shor

  26. Quantum key distribution

  27. Quantum key distribution Uncertainty principle Quantum system cannot be observed without disturbing it

  28. Quantum key distribution

  29. Device-independent quantum cryptography untrusted device

  30. Device-independent quantum cryptography test test test test compute test test untrusted device Strategy 1: Self-testing

  31. Device-independent quantum cryptography test test test test test test test test compute compute test test test test untrusted untrusted device 1 device 2 Strategy 2: Cross-checking

  32. Device-independent quantum cryptography test test test test test test test test compute compute test test test test untrusted untrusted device 1 device 2 Device-independent quantum protocols exist for ● quantum key distribution ● randomness expansion ● randomness amplification

  33. Long-term implications Security vs Privacy

  34. Thank you!

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