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.
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.
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
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