# quantumcrypto

nit jalandhar
7 de Dec de 2014

### quantumcrypto

1. Quantum Cryptography Presented By Tabrej A.Khan 13223006
2. • Classical Cryptography • Introduction to Quantum cryptography- • Classical Cryptography and Key Distribution Problem. • Quantum Communication . • Elements of Quantum Theory • Heisenberg Uncertainty Principle • Quantum Key Distribution . • Detecting Eavesdropper • Technical Challenges of QKD
3. . Classical Cryptography
4. Symmetric Algorithm  Usually use same key for encryption and decryption.  Require sender and receiver to agree on a key before they communicate securely.  Encryption key can be calculated from decryption key and vice versa  Security lies with the key.  Also called secret key algorithms, singlekey algorithms, or one-key algorithms  Example: DES (1977), Triple DES (1998),AES
5. Asymmetric Algorithm  Use different keys for encryption and decryption.  Decryption key cannot be calculated from the encryption key  Anyone can use the key to encrypt data and send it to the host; only the host can decrypt the data  Also known as public key algorithms  Example: Diffie-Hellman (1976) RSA (1977)
6. Vulnerabilities/Weakness to the modern/classical cryptography  There are three main problems with encryption schemes -first is key distribution -the second is key management -Thirdly as computing power increases, and new classical computational techniques are developed, the length of time that a message can be considered secure will decrease, and numerical keys will no longer be able to provide acceptable levels of secure communications
7. Key Distribution Problem  How to communicate the key securely between two pair of users.  it is not possible to check whether this medium was intercepted – and its content copied – or not.  Public key cryptography came as a solution to this, but these too are slow and cannot be used to encrypt large amount of data
8. Elements of Quantum Theory  Light waves are made up of millions of discrete quanta called Photons  They are massless and have energy, momentum and angular momentum called spin.  Spin carries the polarization.
9. Quantum Communication The Classical World - Bits either 0 or 1. - Bits can be copied. - Bits can be observed without changing them. (So, eavesdropping cannot be detected in classical cryptosystems.) Quantum Bits - A quantum bit (qubit) can be 0 or 1 at the same time. - It can not be copied (no cloning theorem). - Its state will collapse if it is observed (measured).  If a qubit can be 0 or 1 at the same time, how many values can n qubits have at the same time ?
10. Quantum Communication  Quantum cryptography solves the key distribution problem by allowing the exchange of a cryptographic key between two remote parties with absolute security, guaranteed by the laws of physics.  Quantum Communication is based on two features of Quantum mechanisms and photons. -State indeterminancy based on Heisenberg principle . -Entangled based protocols that means two entities can be defined such that their properties are entangled altering one effects the value of other.
11. Heisenberg Uncertainty Principle  For any two observable properties linked together like mass and momentum • According to the principle two interrelated properties cannot be measured individually without affecting the other. • Measuring the state of photon will affect it value
12. Quantum Key Distribution – BB84 Protocol
13. Quantum Mechanics for Cryptography – Measurement Basis  Basis – frame of reference for quantum measurement  Example – polarization vertical/horizontal vs. diagonal  Horizontal filter, light gets through = 0  Vertical filter, light gets through = 1  45 deg. filter, light = 0  135 deg. filter, light = 1
14. Quantum Key Distribution – BB84 Protocol
15. Example
16. Detecting Eavesdroppers  To check for the presence of eavesdropping Alice and Bob now compare a certain subset of their remaining bit strings.  If any interceptor has gained any information about the photons polarization, this will have introduced errors in Bobs' measurements  If more than p bits differ they abort the key and try again, possibly with a different quantum channel, as the security of the key cannot be guaranteed.
17. 19 Alice's Bit Sequence 0 1 0 - 0 1 1 1 1 - 1 0 - 1 - - 0 1 - - 1 - 1 0 Bob's Bases Bob's Results Key Alice Bob Polarizers Horizontal - Vertical Diagonal (-45, +45) H/V Basis 45 Basis BB84 protocol: Eve  25% errors
18. Intercept and Resend Attack
19. Implementing Quantum Cryptography(Real Case)  BBN, Harvard, and Boston University built the DARPA quantum network, the world’s first network that delivers end-to-end network security via high-speed quantum key distribution, and tested that network against sophisticated eavesdropping attacks.  For the Bank of Austria, the novel technology was demonstrated by the group of Professor Anton Zeilinger, Vienna University in collaboration with the group Quantum Technologies of Seibersdorf research.  The bank transfer was initiated by Vienna’s Mayor Dr. Michael Haupl, and executed by the director of the Bank Austria Creditanstalt, Dr. Erich.  The information was sent via a glass fiber cable from the Vienna City  Hall to the Bank Austria Creditanstalt branch office “Schottengasse”.
20. TECHNICAL CHALLENGES OF QKD AND FUTURE DIRECTION  One of the challenges for the researchers, is distance limitation.Currently, quantum key distribution distances are limited to tens of kilometers because of optical amplification destroys the qubit state.  Also to develop optical device capable of generating, detecting and guiding single photons; devices that are affordable within a commercial environment .  Also users need reassurance not only that QKD is theoretically sound, but also that it has been securely implemented by the vendors.
21. Summary  Realization of practical quantum information technologies can not be accomplished without involvement of the network research community.  The advances in computer processing power and the threat of limitation for today’s cryptography systems will remain a driving force in the continued research and development of quantum cryptography.  The technology has the potential to make a valuable contribution to the network security among government, businesses, and academic environment.
22. Future Prospects  Ground-to-satellite, satellite-to-satellite links  General improvement with evolving qubit-handling techniques, new detector technologies
23. Thanks