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- Quantum Cryptography Presented By Tabrej A.Khan 13223006
- • 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
- . Classical Cryptography
- 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
- 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)
- 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
- 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
- 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.
- 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 ?
- 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.
- 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
- Quantum Key Distribution – BB84 Protocol
- 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
- Quantum Key Distribution – BB84 Protocol
- Example
- 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.
- 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
- Intercept and Resend Attack
- 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”.
- 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.
- 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.
- Future Prospects Ground-to-satellite, satellite-to-satellite links General improvement with evolving qubit-handling techniques, new detector technologies
- Thanks