Cryptography in a Quantum World

William Mong Distinguished Lecture by Professor Gilles Brassard
Apr 26, 2017

Date:        April 26, 2017 (Wednesday)

Time:       5:00pm – 6:00pm (Reception 4:30pm)

Venue:     Lecture Theatre A, Chow Yei Ching Building, HKU

Speaker:  Professor Gilles Brassard

                 Department of Computer Science and Operations Research

                 Université de Montréal


Cryptography, although practiced as an art and science for thousands of years, had to wait until the end of the 1940s before Claude Shannon gave it a strong mathematical foundation. However, Shannon's approach was rooted in his own information theory, itself inspired by the classical physics of Newton. But our world is ruled by the laws of quantum mechanics. When quantum-mechanical phenomena are considered, new vistas open up both for cryptographers (code makers) and cryptanalysts (code breakers). Some theorems (including by Shannon) remain mathematically correct, but become irrelevant in our quantum world. Most strikingly, it is possible for two people who do not share ahead of time a long secret key to communicate in perfect secrecy under the nose of an eavesdropper with unlimited computing power and whose technology is limited only by the known laws of physics. Conversely, quantum mechanics provides powerful tools to threaten the mechanisms that are currently used on the Internet to protect electronic transactions. Furthermore, it seems — but is not yet proven — that quantum mechanics provides more benefits to cryptanalysts than cryptographers if the latter are restricted to using only classical communication channels. So, in the end, is quantum mechanics a blessing or a curse to the protection of privacy? The jury is still out. No prior knowledge in quantum mechanics or cryptography will be expected from the audience.


Professor of computer science since 1979 and Canada Research Chair at the Université de Montréal, Gilles Brassard FRS, O.C., laid the foundations of quantum cryptography at a time when only a handful of people worldwide were interested in quantum information science. This thirty-year-old theoretical idea has lead to new enabling technologies for secure quantum communication on Earth and via satellite in which China has taken the international lead. Professor Brassard is also among the inventors of quantum teleportation, a universally recognized fundamental keystone of the entire quantum information discipline, for which Thomson Reuters has predicted that he will one day receive the Nobel Prize in Physics. Editor-in-Chief for Journal of Cryptology from 1991 until 1997, he is the author of three books that have been translated into eight languages (including Chinese). He is a Fellow of the Royal Society of London, the Royal Society of Canada, the Canadian Institute for Advanced Research and the International Association for Cryptologic Research. He was awarded honorary doctorates by the ETH in Zürich, the University of Ottawa and the Università della Svizzera italiana in Lugano, and made an Officer of the Order of Canada.


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