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Quantum Cryptography

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by

Jorge Juan Buendía Morales

on 17 December 2013

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Transcript of Quantum Cryptography

Also called Vernam cipher, it is a symmetric algorithm. Given:
an alphabet A = {0, 1 . . . n − 1}
a message m = m1 m2 ··· mL
a key string of the same length k = k1 k2 ··· kL
It produces the ciphertext c = c1 c2 ··· cL
Cryptology:
from Greek
krypt´os
(kryptos), "hidden" and
l´ogos
“word”. The science of secure or generally secret communications. It includes:

- cryptography:
[
krypt´os,
“hidden” and
grap'ein
(graphein), "writing"]

> cryptanalysis: [
krypt´os
, “hidden” and
anal´yein,
“to loosen” or “to untie”].


BB84
ATTACKS AND SECURITY

Emissor/reciever:

Rectilinear (H/V) base:

Diagonal base:

Green:
bit = 1
Red:
bit = 0
QUANTUM CRYPTOGRAPHY
By
Jorge J. Buendía
Héctor López
Sara Peña
Guillem Sanchis
BACKGROUND IN QUANTUM CRYPTOGRAPHY
Max Plancc and the Plancks Constant
THE END
QUANTUM PHYSICS AND GOD
THANK YOU!
What is Quantum Cryptography?
And what is the link with Quantum Cryptography?
SIMULATION
Modern Algorithms
Asymetric Ciphers (RSA):
commonly known as public-key cryptosystems.
The security is based on computational complexity.

Symetric Ciphers:
a single key for both encryption and decryption.
The message is encrypted using randomly generated key.
Phases and fibres
Schrodinger's Cat
BB84: Attacks and security
Different types of balls
BB84: Attacks and security
BB84: Attacks and security
The BB84 protocol
Quantum
information

Heisenberg’s principle
Heisenberg’s principle
How is this information sent?
Photons are used. When a photon is unpolarized, it spins in any possible direction.

Each type of a photon’s spin represents one piece of information- a 1 or a 0.
Quantum cloning attack e = 0.167
Intercept-resend attack e = 0.25
expresses all motion in probability
Optimal attacks: e > 0.146
Photon number splitting attack [Poisson (μ)]
What is Cryptography?
PROTOCOL:
In quantum cryptography Heisenberg’s principle can be used as a great advantage:
Measurements disturb states.
Eavesdropper
Non-cloning theorem
Information in quantum world
Qubits (quantum bits).

As a particle can be at two states simultaneously, information also does.
Quantum cryptography is a method for secure key exchange over an insecure channel based on the nature of photons.

It is the first cryptology that safeguards against passive interceptions.
BACKGROUND
Origin
Vigenère Cipher (Substitution Cipher):
Scytale (Transposition cipher)
World War II ENIGMA Machine:
Terminology
Data Encryption Standard (DES), the plaintext is divided in blocks.
One - time Pad:
If the key string is random and only used once, this is already sufficient to provide
unconditional security
The main problem is key distribution, which has to be at least as secure as the one-time pad itself.

At this point quantum mechanics has provided a completely new opportunity.
Full transcript