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

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

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.