![]() |
Quantum Cryptography full report - Printable Version +- Free Academic Seminars And Projects Reports (https://easyreport.in) +-- Forum: Seminars Topics And Discussions (https://easyreport.in/forumdisplay.php?fid=30) +--- Forum: Miscellaneous Seminars Topics (https://easyreport.in/forumdisplay.php?fid=21) +---- Forum: General Seminar Topics (https://easyreport.in/forumdisplay.php?fid=58) +---- Thread: Quantum Cryptography full report (/showthread.php?tid=46716) |
Quantum Cryptography full report - jeet - 10-04-2017 Quantum Cryptography [attachment=32] Introduction Cryptology, the mathematical science of secret communications, has a long and distinguished history of military and diplomatic uses dating back to the ancient Greeks. 2 In World War II, Allied successes in breaking the ciphers of Germany and Japan played an important part in the outcome of the conflict and the development of the modern computer. 3 Today, the ability to ensure the secrecy of military or diplomatic communications is as vital as ever, but cryptography is also becoming more and more important in everyday life. Cryptography To explain the significance of quantum cryptography it is necessary to describe some of the important features (and perils) of cryptography in general. These points can be illustrated with one of the most famous literary examples of a cipher: Sir Arthur Conan Doyle s The Adventure of the Dancing Men. 1 In this story, Elsie, the American wife of an English gentleman, Hilton Cubbitt, is terrorised by the appearance of chalked stick-figures outside her house. (See Figure 1.) Sherlock Holmes is called in and quickly realises that the figures are not the scribblings of children, but rather are a form of cryptography, in which each letter of the alphabet has been substituted with a stick figure, known only to the sender (Abe Slaney, the most dangerous crook in Chicago ) and the intended recipient, Elsie. Quantum key distribution To understand QKD we must first move away from the traditional key distribution metaphor of Alice sending particular key data to Bob. Instead, we should have in mind a more symmetrical starting point, in which Alice and Bob initially generate their own, independent random number sets, containing more numbers than they need for the key material that they will ultimately share. Next, they compare these sets of numbers to distil a shared subset, which will become the key material. It is important to appreciate that they do not need to identify all of their shared numbers, or even particular ones, because the only requirements on the key material are that the numbers should be secret and random. They can attempt to accomplish a secret distillation if Alice prepares a sequence of tokens, one kind for a 0 and a different kind for a 1 , and sends a token to Bob for each bit in her set. Bob proceeds through his set bit-by-bit in synchronisation with Alice, and compares Alice s token with his bit, and replies to Alice telling her whether the token is the same as his number (but not the value of his bit). Practical implementations of QKD Perhaps the most obvious way to implement the QKD quantum channel is with single-photon polarization states, such as the preparation of vertical and right-handed-circular polarizations, and the measurement of horizontal linear and left-handed-circular polarizations. |