Exploring Quantum Cryptography: Unveiling Secure Transmissions
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Presentation Transcript
Quantum Cryptography Shawn Fanning 4/25/03
Introduction • The study of Quantum Mechanics has opened up new areas of research in cryptographic transmissions, as well as new ideas for classical problems like factoring large numbers.
Topics of Discussion • Quantum Mechanics • Quantum Cryptography (an application) • Peter Shor’s factoring algorithm
2 minute intro to Quantum Mechanics • Polarized light experiment • Bit vs. Qubit • Picture a Qubit as a sphere • Measurement becomes a problem
Quantum Cryptography (an application) • [2] Page 357 (our book) • 2 Channels • Quantum (Fiber optic) • Physical (Normal Wire Comm.) • 2 Bases: B1 and B2 • Alice and Bob each randomly choose Bases • A and B will agree on roughly half of the bits that she sent • Eve ‘forces’ states in action
Factoring on a Quantum Computer • Peter Shor • Church’s Thesis • 2 escape clauses • 1)Physical • 2)Resources • A 3rd resource: precision • IE) 011101101… • Latitude: • 01 deg, 11 min, 01.101 sec
Factoring on a Quantum Computer • L bit number N • Best Classical algorithm (number field sieve) • Quantum Computer [3]
Factoring on a Quantum Computer • 300 digit number [1]: • Best Classical algorithm • (150,000 years at terahertz) • Quantum Computer • (less than a second at terahertz)
Factoring on a Quantum Computer • Recall to factor n: • we want a and r with-- • Quantum Fourier transform • Find the period of a sequence • Repeated squaring until
Real Life • Quantum Cryptography is possible • This has been done (34km) • Quantum Computers/Factoring (??) • Heuristics for skillful play at chess in relation to the game’s basic rules.
References • [1] “Simple Rules for a Complex Quantum World”, Michael A. Nielsoen, Scientific American, May 31,2003 • [2] Introduction to Cryptography, W. Trappe and L.C. Washington, Prentice Hall, 2002 • [3] P. W. Shor, Quantum Computing, IEEE Computer Society Press (1998) • [4] P. W. Shor, Polynomial-time algorithms for prime factorization and discrete logarithms on a quantum computer, SIAM J. Computing 26 (1997) • (The above two papers, as well as much more material by Shor can be found at: www.research.att.com/~shor)
Questions • Comments/Suggestions