Quantum Cryptography ppt

Quantum Cryptography Paper Presentation ppt Full Paper ( Seminar Paper Presentations Materials Projects )

Abstract:During the 20th century and a half, the contest between codemakers and code breakers has undergone reversals and complications. An unbreakable cipher was invented in 1918, although its unbreakability was not proved until the 1940s. This cipher was rather impractical because it required the sender and receiver to agree beforehand on a key - a large stockpile of secret random digits, some of which were used up each time a secret message was transmitted. More practical ciphers with short, reusable keys, or no secret key at all, were developed in the 1970s, but to this day they remain in a mathematical limbo, having neither been broken nor proved secure.
A recent unexpected development is the use of quantum mechanics to perform cryptographic feats unachievable by mathematics alone. Quantum cryptographic devices typically employ individual photons of light and take advantage of Heisenberg's uncertainty principle, according to which measuring a quantum system in general disturbs it and yields incomplete information about its state before the measurement. Eavesdropping on a quantum communications channel therefore causes an unavoidable disturbance, alerting the legitimate users. Quantum cryptography exploits this effect to allow two parties who have never met and who share no secret information beforehand to communicate in absolute secrecy under the nose of an adversary.

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