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Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy
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Page 1: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

Quantum CryptographyPost Tenebras Lux!

Grégoire Ribordy

Page 2: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

www.idquantique.com

Outline Introduction: Cryptography

Quantum Information Processing

Quantum cryptography protocole

Practical system

Applications and outlook

Page 3: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

www.idquantique.com

Cryptography

0101110100011011

Document

KeyEncryption

Decryption0101110100011011

Document

KeySecure communication

Key transmission

AliceBob

Eve

Key generation

Page 4: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

www.idquantique.com

Secret key cryptography Encryption and decryption key identical

Problem: Key exchange

The longer the key, the higher the security– One-time pad

Page 5: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Public key cryptography

Encryption key Decryption key(public) (private)

One way function

Key distribution problem solved?

Caution: vulnerable– Mathematical progress:

Security is based on mathematical assumptions– Technological progress:

Computers become more powerful

La Poste

13 31 = 403

Page 6: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Computational complexity Complexity of a computer program…

P(n) = n + n2 + n3+…+nk E(n) = exp (n) = n + n2 + n3 + n4 … + n

In cryptography

Key length

Co

mp

uti

ng

tim

e

EncryptionDecryption

Key length

Co

mp

uti

ng

tim

e

Decryption(without key)

Key length

Co

mp

uti

ng

tim

e

Theoretical progress

Key length

Co

mp

uti

ng

tim

e

Quantum computer

Classical computer

Page 7: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Another look at Moore’s Law Trend of computer chip development

hit a « quantum wall »

Potential of quantum physics not yet exploited in industrial applications

1

10

100

1000

10000

100000

1970 1980 1990 2000 2010 2020

Year

Tra

nsi

sto

rs p

er c

hip

[x10

00]

0

10

20

30

40

50

Siz

e o

f tr

ansi

sto

r's

gri

d

[ato

ms]

Quantum Limit

Page 8: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Quantum Physics and Cryptography

0101110100011011

Document

KeyEncryption

Decryption0101110100011011

Document

KeySecure communication

AliceBob

Eve

Key generation

Public key cryptography cracking

Key transmission

Page 9: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

www.idquantique.com

Quantum Random Number Generator Physical randomness source

Commercially available Applications

– Cryptography– Numerical simulations– Statistics

Page 10: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

www.idquantique.com

Quantum Physics and Cryptography

0101110100011011

Document

KeyEncryption

Decryption0101110100011011

Document

KeySecure communication

Key transmission

AliceBob

Eve

Key generation

Public key cryptography cracking

Page 11: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

www.idquantique.com

Classical vs quantum communications Communication System

Secure channel over dedicated optical fiber– Absolute security guaranteed by the laws of quantum

physics

"0""1""1" Fragile !

Page 12: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Quantum communications Transmitting information with a single-photon

E

Light Polarization Linear States

= "0"

= "1"

Page 13: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Eavesdropping (1) A single-photon constitutes an elementary quantum

system

It cannot be split

Semi-transparent mirror

?

?

50%

50%

Page 14: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Eavesdropping (2) Communication interception

Use quantum physics to force spy to introduce errors in the communication

?"0" "0"

Eve

BobAlice

Page 15: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Polarization measurement Using polarizing filters to measure polarization states

and

and

and ?

= "0"

= "1"

= "0"

= "1"Base 1 Base 2

But• probabilistic

• modification

Heisenberg’s Uncertainty Relations

Page 16: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Quantum Cryptography Protocole BB84

A better name: Quantum Key Distribution

A lice 's B it S e q u e n c e

0 1 0 - 0 1 1 1 1 - 1 0

- 1 - - 0 1 - - 1 - 1 0

B o b 's B a s e s

B o b 's R e s u lts

K e y

A lice

B o b

P o la riz e r s

H o r iz o n ta l - Ve rtic a l

D ia g o n a l ( -4 5 , + 4 5 )

H /V B a s is

4 5 B a s is

Page 17: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Key Distillation (ideal case)

Alice BobQuantum channel

Qubits

Transmission

Basis

Reconciliation

QBERestimate

QBER =0 : no eavesdropping

> 0 : eavesdropping

Sifted key

Reveals rather than prevents eavesdropping

A better name: quantum key distributionquantum key distribution

Page 18: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

www.idquantique.com

Key Distillation (realistic case)

Alice BobQuantum channel

Public channel

(losses)

Qubits

Transmission

Basis

Reconciliation

QBERestimate

Error

correctionPrivacy

amplification

Sifted key

Raw key

Key Key

Page 19: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Implementing the quantum channel Necessary components

ChannelSingle-Photon Source

Single-Photon Detector

Page 20: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Quantum Cryptography System

• Collaboration: id Quantique – UniGe• Pilot tests in 2003

Page 21: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Field tests

Optical fibers

Distance: 67 km

Genève – Lausanne

Page 22: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Deployment

QKD Hardware QKD Hardware

Optical Fiber(classical channel)

Computernetwork A

Computernetwork B

Key exchange

Quantum channel

Encryption

Decryption

Classical channel

Traffic Network A to B

Traffic Network B to A

Encryptedtraffic

Encryptedtraffic

Optical Fiber(quantum channel)

Main features- Encryption

- Transparent- High-bit rate (1 Gbit/s)

- Remote monitoring- Automated key management

Page 23: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

www.idquantique.com

Applications Advantages

– Automated key management– Long term security

Constraints– Optical fiber– Distance < 100 km

High-security applications in a metropolitan area network– Financial sector, e-government– Storage, disaster recovery

Page 24: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Extending the distance Secure relays

Improved components– Photon counting detectors

– Photonic crystal fibers: 0.2 dB/km 0.02 dB/km

Quantum repeater

Free-space links to satellites

Page 25: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Quantum Teleportation– Quantum version of a fax

– Recently at Unige: teleportation

of a photon over 2km

Rudimentary quantum repeater

Quantum Repeater

01100111010101000110010

Page 26: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

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Free-space QKD Satellites = secure relay

Experiments over horizontal links– 23.4 km in the German Alps

GenèveTokyo

Page 27: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

www.idquantique.com

Post Tenebras Lux?

Page 28: Quantum Cryptography Post Tenebras Lux! Grégoire Ribordy.

www.idquantique.com

Thank you for your attention

id Quantique SA

Chemin de la Marbrerie, 3

CH-1227 Carouge / Geneva

Switzerland

Ph: +41 22 301 83 71

Fax: +41 22 301 83 79

[email protected]

www.idquantique.com