quantum key distribution

Quantum KeyDistribution

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Introduction

ClassicalCryptography

QuantumCryptography


Pros and Cons

Conclusion

Quantum Key Distribution In QuantumCryptography

Shahrukh Ayaz KhanSeminar Presentation

SSBT’s College of Engineering & Technology,Bambhori, Jalgaon - 425 001, Maharashtra, India

October 6, 2015

April 10, 2015 Shahrukh Ayaz Khan Quantum Key Distributionl 1/26


Outline

Introduction


QuantumCryptography


Pros and Cons

Conclusion

Presentation Outline

1 Introduction

2 Classical Cryptography

3 Quantum Cryptography

4 Quantum Key Distribution

5 Pros and Cons

6 Conclusion



Outline

Introduction


QuantumCryptography


Pros and Cons

Conclusion

Outline

1 Introduction




5 Pros and Cons

6 Conclusion



Outline

Introduction


QuantumCryptography


Pros and Cons

Conclusion

What is Cryptography?

Cryptography: the coding and decoding of secretmessages.

Cryptography is the art of rendering a messageunintelligible to any unauthorized party

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It is part of the broader field of cryptology, which alsoincludes cryptoanalysis, the art of code breaking



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QuantumCryptography


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Need For Cryptography

Suppose Alice want to send a secret message to his friendBob over an insecure channel

we have to prevent Eve from Eavesdropping oncommunication between Alice and Bob.

Figure: Meet Alice and Bob



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QuantumCryptography


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1 Introduction




5 Pros and Cons

6 Conclusion



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QuantumCryptography


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Cryptography

What is key?

Encryption is combine a message with some additionalinformation - known as the key and produce acryptogram.

Decryption is combine a cryptogram with some additionalinformation - known as the key and produce a message.



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Types of Cryptosystems

Symmetric - use the same (secret) key to encrypt anddecrypt a message

Asymmetric - use one key (the public key) to encrypt amessage and a different key (the private key) to decrypt it.Asymmetric cryptosystems are also called public keycryptosystems.

Figure: Process of cryprography



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QuantumCryptography


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One-Time Pad

first proposed by Gilbert Vernam in 1926This cryptosystem is thus provably secure in the sense ofinformation theory (Shannon 1949)Actually, this is today the only provably securecryptosystemOnly problem is distributing the keys and it is Difficult toimplement

Figure: One time pad



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Introduction


QuantumCryptography


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1 Introduction




5 Pros and Cons

6 Conclusion



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QuantumCryptography


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Need of Quantum Cryptography?

The problem of distributing the keys in the OTP isovercomed in Quantum Key Distribution

Using quantum effects, we can distribute keys in perfectsecrecy!

The Result is Perfect Cryptosystem, QC = QKD + OTP

Classical Cryptography relies heavily on the complexity offactoring integers.

Quantum Computers can use Shors Algorithm toefficiently break todays cryptosystems



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QuantumCryptography


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Quantum Elements

Quantum Mechanics depends on 2 major elements of quantummechanics: i.e heisenberg uncertainity principle and principle ofphoton polarization.

Heisenberg uncertainty principle : states that certain pairsof physical properties are related in such a way thatmeasuring one property prevents the observer fromsimultaneously knowing the value for other.Principle of photon polarization: tells that aneavesdropper cannot copy unknown Qubits due tonon-cloning algorithm.

Figure: Polarization of Light



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QuantumCryptography


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Overview of Quantum Cryptography

Unique property of quantum cryptography is the ability oftwo communicating users to detect the presence of thirdparty trying to gain knowledge of the key.By using quantum superposition/entanglement andtransmitting information in quantum states , acommunication system can be implemented which candetect eavesdropping.The polarization basis is the mapping we decide to use fora particular stateEntangled pairs of photon are used that affectsrandomness of measurements

Figure: Photon Polarization using BasesApril 10, 2015 Shahrukh Ayaz Khan Quantum Key Distributionl 13/26


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Introduction


QuantumCryptography


Pros and Cons

Conclusion

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1 Introduction




5 Pros and Cons

6 Conclusion



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Introduction


QuantumCryptography


Pros and Cons

Conclusion

Quantum Key Distribution

Quantum Key Distribution exploits the effects discussed inorder to thwart eavesdropping.

It enables two parties to produce a shared random bitstring known only to them, which can be used as a key forencryption and decryption.

If an eavesdropper uses the wrong polarization basis tomeasure the channel, the result of the measurement willbe random.

There are three main security protocols for QKD: BB84,B92, and Entanglement-Based QKD.

We will only discuss BB84 here.



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QuantumCryptography


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BB84

BB84 was the first security protocol implementingQuantum Key Distribution.

The key consists of bits that will be transmitted asphotons.

Each bit is encoded with a random polarization basis!

Alice and Bob talk on the telephone:

Alice chooses a subset of the bits (the test bits) andreveals which basis she used to encode them to Bob.

Bob tells Alice which basis he used to decode the samebits.

Where the same basis was used, Alice tells Bob what bitshe ought to have got.



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QuantumCryptography


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BB84 with no Eavesdropping

The test bits allow Alice and Bob to test whether the channelis secure.

Figure: Comparing measurements Alices BitApril 10, 2015 Shahrukh Ayaz Khan Quantum Key Distributionl 17/26


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Cont..

Figure: Getting the Final Key



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BB84 with Eavesdropping

If an eavesdropper Eve tries to tap the channel, this willautomatically show up in Bobs measurements.

In those cases where Alice and Bob have used the samebasis, Bob is likely to obtain an incorrect measurement

As Eve intercepts Alices photons, she has to measure themwith a random basis and send new photons to Bob.

The photon states cannot be cloned (non-cloneability).



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QuantumCryptography


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5 Pros and Cons

6 Conclusion



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QuantumCryptography


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Merits

Nearly Impossible to stealDetect if someone is listeningSecure

Limitations

Price limits length,signal is absorbed, noise increasedAvailabilityCompete with traditional networks



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Future Scope

Future applications are in the most secure communication linesfor bank-to-ATM transactions, financial information protectionover the internet, and military and government communicationsincluding the use for ship-to-ship, ground-to-satellite, andsatellite-to-satellite communication.



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Introduction


QuantumCryptography


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5 Pros and Cons

6 Conclusion



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QuantumCryptography


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Conclusion

Quantum cryptography is a major achievement in securityengineering.

As it gets implemented, it will allow perfectly secure banktransactions, secret discussions for government officials,and well-guarded trade secrets for industry!



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QuantumCryptography


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References

1 N. Namekata, S. Mori, and S. Inoue, Quantum keydistribution over an installed multimode optical fiber localarea network, Optical Express, 2015.

2 A. Beresford and F. Stajano, Location privacy in pervasivecomputing, IEEE Pervasive Computing, 2011.

3 K. G. Paterson, F. Piper, and R. Schack, Why quantumcryptography?, Quantum physics, quant-ph/0406147,June 2004.

4 Hidema Tanaka, Security Analysis of GeneralizedConfidential Modulation for Quantum CommunicationInternational Journal of Computer Networks &Communications (IJCNC) Vol.5, No.5, September 2013



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Thank You...ShahrukhA.Khan
