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ABSTRACT: The advent of real functional quantum computers will cause a privacy problem. Indeed, quantum computers are particularly good at solving algorithms that ensure information privacy, like the RSA algorithm. In this talk, we will see how quantum computers can be used to restore unconditional security and privacy. BIO: Nicolò Leone is a Postdoctoral researcher at the Department of Physics of the University of Trento. He has obtained his PhD in 2022. His research interests are quantum information and integrated photonics.

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- 1. The privacy in the era of quantum computers Dr. Nicolò Leone nicolo.leone@unitn.it 21/03/23 NanoScience Laboratory
- 2. Quantum computers are great!!! Solve different kinds of classically unsolvable problems.
- 3. Any downside? The title of the presentation has spoiled it…
- 4. Based on Public key cryptography system Sharing of information
- 5. Based on assumption The considered problem is hard to be solved by classical computers Public key cryptography Public Private Connected by the algorithm Es: the public key = product of the two prime numbers Alice Bob Alice
- 6. Based on assumption The considered problem is hard to be solved by classical computers Public key cryptography Encrypted with Alice Public key Alice Bob
- 7. Based on assumption The considered problem is hard to be solved by classical computers Public key cryptography Alice decrypts the message using his private key. Factorisation of large prime numbers. Solved in exponential time Alice Bob
- 9. Solve factorisation problems Quantum Computers Can solve other crypto. problems? Algorithm Only a few Future Not enough qubit Time Polynomial Security Cannot simply take a longer key https://newsroom.ibm.com/media-quantum-innovation?keywords=quantum&l=100
- 10. Time is passing. The company are approaching the number of necessary qubits. https://newsroom.ibm.com/media-quantum-innovation?keywords=quantum&l=100
- 11. Post-quantum cryptography Find problems that are still difficult to be solved by quantum computers Quantum cryptography Using quantum physics to beat quantum physics.
- 13. PRO Quantum cryptography Quantum key distribution CONS Deployment Hardware Cost Expensive Security Quantum mechanics Demanding Dedicated hardware https://www.qticompany.com/products/
- 14. BB84 First protocol proposed by Bennett and Bressard in 1984 Quantum key distribution The key is not transmitted Alice Bob
- 15. Quantum channel Channel in which we inject the quantum light Quantum key distribution Alice Bob
- 16. Polarization Direction of oscillation of the electronic field Quantum key distribution 0 1 B1 B2 B1 B2 Alice Bob
- 17. Input randomness It is necessary to randomly select the base and the digit to send Quantum key distribution 0 1 B1 B2 B1 B2 Alice Bob
- 18. Input randomness Bob needs to select its measurement basis also randomly. Quantum key distribution 0 1 B1 B2 B1 B2 Alice Bob
- 19. Quantum collapse Bob projects the wavefunction of the photon. Quantum key distribution ℙ(V) = 1
- 20. Quantum collapse Bob projects the wavefunction of the photon. Quantum key distribution ℙ(V) = 1 ℙ(V) = 0.5 ℙ(H) = 0.5
- 21. Now let’s enter in the protocol Quantum key distribution #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 Alice Base B1 B2 B1 B1 B2 B1 B1 B2 B2 B1 Alice Digit 0 1 1 0 0 1 0 1 1 0 Bob Base B1 B1 B1 B2 B1 B1 B2 B2 B2 B2 Bob Result 0 X 1 X X 1 X 1 1 X Alice Bob
- 22. Now let’s enter in the protocol Quantum key distribution #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 Alice Base B1 B2 B1 B1 B2 B1 B1 B2 B2 B1 Alice Digit 0 1 1 0 0 1 0 1 1 0 Bob Base B1 B1 B1 B2 B1 B1 B2 B2 B2 B2 Bob Result 0 X 1 X X 1 X 1 1 X Alice Bob
- 23. Basis announcement They keep the runs in which the basis are the same. Quantum key distribution Alice and Bob announce the basis used. Alice Bob
- 24. The key creation Bob and Alice have obtained the same key Quantum key distribution #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 Alice Base B1 B1 B1 B2 B2 Alice Digit 0 1 1 1 1 Bob Base B1 B1 B1 B2 B2 Bob Result 0 1 1 1 1 Alice Bob
- 25. The appearance of Eve Now an Eavesdropper appears and try to steal the key. Quantum key distribution Alice Bob Eve
- 26. The appearance of Eve Now an Eavesdropper appears and try to steal the key. Quantum key distribution Alice Bob Eve
- 27. Eve performs an intercept and resend attack Eve chooses the right base. Quantum key distribution
- 28. Eve performs an intercept and resend attack Eve chooses the wrong base. Eve introduces errors in the sequence. Quantum key distribution
- 29. Eve action Errors are introduced in the sequence. Quantum key distribution #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 Alice Base B1 B2 B1 B1 B2 B1 B1 B2 B2 B1 Alice Digit 0 1 1 0 0 1 0 1 1 0 Bob Base B1 B1 B1 B2 B1 B1 B2 B2 B2 B2 Bob Result 1 X 1 X X 1 X 0 0 X Alice Bob
- 30. Error estimation Alice and Bob share a piece of their key. Quantum key distribution Error estimation, by comparing a piece of the key. Alice Bob
- 31. Error estimation All the errors are treated as due to Eve. Quantum key distribution Errors < Threshold_value Alice Bob
- 32. One-time pad A method that is 100% secure. Quantum key distribution Encrypted message B = 01000010 01000010 + 01100001 = 00100011 Key = 01100001 # 00100011 + 01100001 = 01000010 Key = 01100001 # = 00100011 B Alice Bob
- 33. One-time pad Never reuse the same key! Quantum key distribution V V From: http://www.cryptosmith.com/archives/70 = = = V V From: http://www.cryptosmith.com/archives/70 = =
- 34. Secure forever! It is theoretically the most secure approach that can be implemented. The attacks are unfeasible It is better to try to compromise Alice or Bob Cost reduction A As the research proceeds the cost of the QKD will decrease Quantum-key distribution
- 35. Actually testing a new prototype of bidirectional QKD system Now
- 36. Find out more SPEQK Team info@speqk.com
- 37. |ψ⟩ = 1 2 (|Thank⟩ + |you⟩)