PowerPoint PresentationMenuWhat is a “Protocol”?AlgorithmSlide 5What is a Protocol?Jargon File 4.2.0What is a Cryptographic Protocol?Algorithm, Protocol, Cryptographic Protocol?What is Computer Science?Slide 11Slide 12Slide 13What is the difference between Euclid and Ada?Geometry vs. Computer ScienceComputer ScienceCS 200Visual CryptographySlide 19Key + CiphertextPerfect Cipher?Perfect CipherQuantum CryptographyQuantum Physics for DummiesHeisenberg’s Uncertainty PrincipleQuantum CashPhoton PolarityPhoton StreamSlide 29Bank Verifies BillCounterfeiting Quantum CashPerfect Security?Guessing One +45º PhotonQuantum Key DistributionSlide 35Slide 36Detecting PhotonsFinding Correct GuessesWhat about Eve?Eve is CaughtPractical Quantum CryptographySlide 42Though AirWhat’s in the “Sneakers” Black Box?Quantum ComputingSummary/ChargeDavid Evanshttp://www.cs.virginia.edu/~evansCS588: Security and PrivacyUniversity of VirginiaComputer ScienceLecture 16:Blocking and Catching Photons7 Nov 2001 University of Virginia CS 588 2Menu•Trick-or-Treat “Answers”•Visual Cryptography•Quantum Cryptography•Quantum Computing7 Nov 2001 University of Virginia CS 588 3What is a “Protocol”?What is an “Algorithm”?7 Nov 2001 University of Virginia CS 588 4Algorithm•David Harel: “The ingredients are the inputs to the process, the cake is its output, and the recipe is the algorithm.”•Garrett (MBC): “A computational or decision-making procedure that can be completely automated.”7 Nov 2001 University of Virginia CS 588 5Algorithm•The American Heritage Dictionary of the English Language: “A step-by-step problem-solving procedure, especially an established, recursive computational procedure for solving a problem in a finite number of steps.”7 Nov 2001 University of Virginia CS 588 6What is a Protocol?An algorithm involving 2 or more parties.Schneier: “A series of steps, involving two or more parties, designed to accomplish a task.”Garrett (MBC):7 Nov 2001 University of Virginia CS 588 7Jargon File 4.2.0protocol n. As used by hackers, this never refers to niceties about the proper form for addressing letters to the Papal Nuncio or the order in which one should use the forks in a Russian-style place setting; hackers don't care about such things. It is used instead to describe any set of rules that allow different machines or pieces of software to coordinate with each other without ambiguity. So, for example, it does include niceties about the proper form for addressing packets on a network or the order in which one should use the forks in the Dining Philosophers Problem. It implies that there is some common message format and an accepted set of primitives or commands that all parties involved understand, and that transactions among them follow predictable logical sequences.7 Nov 2001 University of Virginia CS 588 8What is a Cryptographic Protocol?A protocol involving one or more secrets.7 Nov 2001 University of Virginia CS 588 9Algorithm, Protocol, Cryptographic Protocol?TCPDatingDining at McDonald’sDining at Hamilton’sJapanese Tea CeremonyTrick-or-Treating…7 Nov 2001 University of Virginia CS 588 10What is Computer Science?“The Chinese tea ceremony, unlike the Japanese tea ceremony, emphasizes the tea, rather than the ceremony.”http://desires.com/1.4/Food/Docs/tea.html7 Nov 2001 University of Virginia CS 588 11Let AB and CD be the two given numbers not relatively prime. It is required to find the greatest common measure of AB and CD.If now CD measures AB, since it also measures itself, then CD is a common measure of CD and AB. And it is manifest that it is also the greatest, for no greater number than CD measures CD. But, if CD does not measure AB, then, when the less of the numbers AB and CD being continually subtracted from the greater, some number is left which measures the one before it.7 Nov 2001 University of Virginia CS 588 12For a unit is not left, otherwise AB and CD would be relatively prime, which is contrary to the hypothesis. Therefore some number is left which measures the one before it. Now let CD, measuring BE, leave EA less than itself, let EA, measuring DF, leave FC less than itself, and let CF measure AE. Since then, CF measures AE, and AE measures DF, therefore CF also measures DF. But it measures itself, therefore it also measures the whole CD. But CD measures BE, therefore CF also measures BE. And it also measures EA, therefore it measures the whole BA. But it also measures CD, therefore CF measures AB and CD. Therefore CF is a common measure of AB and CD.I say next that it is also the greatest. If CF is not the greatest common measure of AB and CD, then some number G, which is greater than CF, measures the numbers AB and CD. Now, since G measures CD, and CD measures BE, therefore G also measures BE. But it also measures the whole BA, therefore it measures the remainder AE. But AE measures DF, therefore G also measures DF. And it measures the whole DC, therefore it also measures the remainder CF, that is, the greater measures the less, which is impossible. Therefore no number which is greater than CF measures the numbers AB and CD. Therefore CF is the greatest common measure of AB and CD.Euclid’s Elements, Book VII, Proposition 2 (300BC)7 Nov 2001 University of Virginia CS 588 13By the word operation, we mean any process which alters the mutual relation of two or more things, be this relation of what kind it may. This is the most general definition, and would include all subjects in the universe. Again, it might act upon other things besides number, were objects found whose mutual fundamental relations could be expressed by those of the abstract science of operations, and which should be also susceptible of adaptations to the action of the operating notation and mechanism of the engine... Supposing, for instance, that the fundamental relations of pitched sounds in the science of harmony and of musical composition were susceptible of such expression and adaptations, the engine might compose elaborate and scientific pieces of music of any degree of complexity or extent.Ada, Countess of Lovelace, around 18307 Nov 2001 University of Virginia CS 588 14What is the difference between Euclid and Ada?“It depends on what your definition of ‘is’ is.” Bill Gates(speaking at Microsoft’s anti-trust trial)7 Nov 2001 University of Virginia CS 588 15Geometry vs. Computer Science•Geometry (mathematics) is about declarative knowledge: