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← Cryptographers, quantum computers and the war for information

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Showing Revision 8 created 11/12/2019 by Oliver Friedman.

  1. I'm in the business
    of safeguarding secrets,
  2. and this includes your secrets.
  3. Cryptographers are
    the first line of defense

  4. in an ongoing war that's been
    raging for centuries:
  5. a war between code makers
  6. and code breakers.
  7. And this is a war on information.
  8. The modern battlefield
    for information is digital.
  9. And it wages across your phones,
  10. your computers
  11. and the internet.
  12. Our job is to create systems that scramble
    your emails and credit card numbers,
  13. your phone calls and text messages --
  14. and that includes those saucy selfies --
  15. (Laughter)

  16. so that all of this information
    can only be descrambled

  17. by the recipient that it's intended for.
  18. Now, until very recently,

  19. we thought we'd won this war for good.
  20. Right now, each of your smartphones
    is using encryption
  21. that we thought was unbreakable
    and that was going to remain that way.
  22. We were wrong,
  23. because quantum computers are coming,
  24. and they're going to change
    the game completely.
  25. Throughout history,
    cryptography and code-breaking

  26. has always been this game
    of cat and mouse.
  27. Back in the 1500s,
  28. Queen Mary of the Scots thought
    she was sending encrypted letters
  29. that only her soldiers could decipher.
  30. But Queen Elizabeth of England,
  31. she had code breakers
    that were all over it.
  32. They decrypted Mary's letters,
  33. saw that she was attempting
    to assassinate Elizabeth
  34. and, subsequently,
    they chopped Mary's head off.
  35. A few centuries later, in World War II,
  36. the Nazis communicated
    using the Engima code,
  37. a much more complicated encryption scheme
    that they thought was unbreakable.
  38. But then good old Alan Turing,
  39. the same guy who invented
    what we now call the modern computer,
  40. he built a machine and used it
    to break Enigma.
  41. He deciphered the German messages
  42. and helped to bring Hitler
    and his Third Reich to a halt.
  43. And so the story has gone
    throughout the centuries.
  44. Cryptographers improve their encryption,
  45. and then code breakers fight back
    and they find a way to break it.
  46. This war's gone back and forth,
    and it's been pretty neck and neck.
  47. That was until the 1970s,

  48. when some cryptographers
    made a huge breakthrough.
  49. They discovered an extremely
    powerful way to do encryption
  50. called "public-key cryptography."
  51. Unlike all of the prior methods used
    throughout history, it doesn't require
  52. that the two parties that want to send
    each other confidential information
  53. have exchanged the secret key beforehand.
  54. The magic of public-key cryptography
    is that it allows us to connect securely
  55. with anyone in the world,
  56. whether we've exchanged
    data before or not,
  57. and to do it so fast that you and I
    don't even realize it's happening.
  58. Whether you're texting your mate
    to catch up for a beer,
  59. or you're a bank that's transferring
    billions of dollars to another bank,
  60. modern encryption enables us
    to send data that can be secured
  61. in a matter of milliseconds.
  62. The brilliant idea that makes
    this magic possible,

  63. it relies on hard mathematical problems.
  64. Cryptographers are deeply interested
    in things that calculators can't do.
  65. For example, calculators can multiply
    any two numbers you like,
  66. no matter how big the size.
  67. But going back the other way --
  68. starting with the product and then asking,
  69. "Which two numbers multiply
    to give this one?" --
  70. that's actually a really hard problem.
  71. If I asked you to find which two-digit
    numbers multiply to give 851,
  72. even with a calculator,
  73. most people in this room would have
    a hard time finding the answer
  74. by the time I'm finished with this talk.
  75. And if I make the numbers a little larger,
  76. then there's no calculator on earth
    that can do this.
  77. In fact, even the world's
    fastest supercomputer
  78. would take longer
    than the life age of the universe
  79. to find the two numbers
    that multiply to give this one.
  80. And this problem,
    called "integer factorization,"
  81. is exactly what each of your smartphones
    and laptops is using right now
  82. to keep your data secure.
  83. This is the basis of modern encryption.
  84. And the fact that all the computing power
    on the planet combined can't solve it,
  85. that's the reason we cryptographers
    thought we'd found a way
  86. to stay ahead of the code
    breakers for good.
  87. Perhaps we got a little cocky

  88. because just when we thought
    the war was won,
  89. a bunch of 20th-century physicists
    came to the party,
  90. and they revealed
    that the laws of the universe,
  91. the same laws that modern
    cryptography was built upon,
  92. they aren't as we thought they were.
  93. We thought that one object couldn't be
    in two places at the same time.
  94. It's not the case.
  95. We thought nothing can possibly spin
    clockwise and anticlockwise
  96. simultaneously.
  97. But that's incorrect.
  98. And we thought that two objects
    on opposite sides of the universe,
  99. light years away from each other,
  100. they can't possibly influence
    one another instantaneously.
  101. We were wrong again.
  102. And isn't that always the way
    life seems to go?

  103. Just when you think you've got
    everything covered, your ducks in a row,
  104. a bunch of physicists come along
  105. and reveal that the fundamental laws
    of the universe are completely different
  106. to what you thought?
  107. (Laughter)

  108. And it screws everything up.

  109. See, in the teeny tiny subatomic realm,

  110. at the level of electrons and protons,
  111. the classical laws of physics,
  112. the ones that we all know and love,
  113. they go out the window.
  114. And it's here that the laws
    of quantum mechanics kick in.
  115. In quantum mechanics,
  116. an electron can be spinning clockwise
    and anticlockwise at the same time,
  117. and a proton can be in two places at once.
  118. It sounds like science fiction,
  119. but that's only because
    the crazy quantum nature of our universe,
  120. it hides itself from us.
  121. And it stayed hidden from us
    until the 20th century.
  122. But now that we've seen it,
    the whole world is in an arms race
  123. to try to build a quantum computer --
  124. a computer that can harness the power
    of this weird and wacky quantum behavior.
  125. These things are so revolutionary

  126. and so powerful
  127. that they'll make today's
    fastest supercomputer
  128. look useless in comparison.
  129. In fact, for certain problems
    that are of great interest to us,
  130. today's fastest supercomputer
    is closer to an abacus
  131. than to a quantum computer.
  132. That's right, I'm talking about
    those little wooden things with the beads.
  133. Quantum computers can simulate
    chemical and biological processes
  134. that are far beyond the reach
    of our classical computers.
  135. And as such, they promise to help us solve
    some of our planet's biggest problems.
  136. They're going to help us
    combat global hunger;
  137. to tackle climate change;
  138. to find cures for diseases and pandemics
    for which we've so far been unsuccessful;
  139. to create superhuman
    artificial intelligence;
  140. and perhaps even more important
    than all of those things,
  141. they're going to help us understand
    the very nature of our universe.
  142. But with this incredible potential

  143. comes an incredible risk.
  144. Remember those big numbers
    I talked about earlier?
  145. I'm not talking about 851.
  146. In fact, if anyone in here
    has been distracted
  147. trying to find those factors,
  148. I'm going to put you out of your misery
    and tell you that it's 23 times 37.
  149. (Laughter)

  150. I'm talking about the much
    bigger number that followed it.

  151. While today's fastest supercomputer
    couldn't find those factors
  152. in the life age of the universe,
  153. a quantum computer
    could easily factorize numbers
  154. way, way bigger than that one.
  155. Quantum computers will break
    all of the encryption currently used

  156. to protect you and I from hackers.
  157. And they'll do it easily.
  158. Let me put it this way:
  159. if quantum computing was a spear,
  160. then modern encryption,
  161. the same unbreakable system
    that's protected us for decades,
  162. it would be like a shield
    made of tissue paper.
  163. Anyone with access to a quantum computer
    will have the master key
  164. to unlock anything they like
    in our digital world.
  165. They could steal money from banks
  166. and control economies.
  167. They could power off hospitals
    or launch nukes.
  168. Or they could just sit back
    and watch all of us on our webcams
  169. without any of us knowing
    that this is happening.
  170. Now, the fundamental unit of information
    on all of the computers we're used to,

  171. like this one,
  172. it's called a "bit."
  173. A single bit can be one of two states:
  174. it can be a zero or it can be a one.
  175. When I FaceTime my mum
    from the other side of the world --
  176. and she's going to kill
    me for having this slide --
  177. (Laughter)

  178. we're actually just sending each other
    long sequences of zeroes and ones

  179. that bounce from computer to computer,
    from satellite to satellite,
  180. transmitting our data at a rapid pace.
  181. Bits are certainly very useful.
  182. In fact, anything
    we currently do with technology
  183. is indebted to the usefulness of bits.
  184. But we're starting to realize
  185. that bits are really poor at simulating
    complex molecules and particles.
  186. And this is because, in some sense,
  187. subatomic processes can be doing
    two or more opposing things
  188. at the same time
  189. as they follow these bizarre rules
    of quantum mechanics.
  190. So, late last century,

  191. some really brainy physicists
    had this ingenious idea:
  192. to instead build computers
    that are founded
  193. on the principles of quantum mechanics.
  194. Now, the fundamental unit of information
    of a quantum computer,
  195. it's called a "qubit."
  196. It stands for "quantum bit."
  197. Instead of having just two states,
    like zero or one,
  198. a qubit can be an infinite
    number of states.
  199. And this corresponds to it being
    some combination of both zero and one
  200. at the same time,
  201. a phenomenon that we call "superposition."
  202. And when we have two qubits
    in superposition,
  203. we're actually working across
    all four combinations
  204. of zero-zero, zero-one,
    one-zero and one-one.
  205. With three qubits,
  206. we're working in superposition
    across eight combinations,
  207. and so on.
  208. Each time we add a single qubit,
    we double the number of combinations
  209. that we can work with in superposition
  210. at the same time.
  211. And so when we scale up
    to work with many qubits,
  212. we can work with an exponential
    number of combinations
  213. at the same time.
  214. And this just hints at where the power
    of quantum computing is coming from.
  215. Now, in modern encryption,

  216. our secret keys, like the two factors
    of that larger number,
  217. they're just long sequences
    of zeroes and ones.
  218. To find them,
  219. a classical computer must go through
    every single combination,
  220. one after the other,
  221. until it finds the one that works
    and breaks our encryption.
  222. But on a quantum computer,
  223. with enough qubits in superposition,
  224. information can be extracted
    from all combinations at the same time.
  225. In very few steps,
  226. a quantum computer can brush aside
    all of the incorrect combinations,
  227. home in on the correct one
  228. and then unlock our treasured secrets.
  229. Now, at the crazy quantum level,

  230. something truly incredible
    is happening here.
  231. The conventional wisdom
    held by many leading physicists --
  232. and you've got to stay
    with me on this one --
  233. is that each combination is actually
    examined by its very own quantum computer
  234. inside its very own parallel universe.
  235. Each of these combinations,
    they add up like waves in a pool of water.
  236. The combinations that are wrong,
  237. they cancel each other out.
  238. And the combinations that are right,
  239. they reinforce and amplify each other.
  240. So at the end of the quantum
    computing program,
  241. all that's left is the correct answer,
  242. that we can then observe
    here in this universe.
  243. Now, if that doesn't make
    complete sense to you, don't stress.

  244. (Laughter)

  245. You're in good company.

  246. Niels Bohr, one of
    the pioneers of this field,
  247. he once said that anyone
    who could contemplate quantum mechanics
  248. without being profoundly shocked,
  249. they haven't understood it.
  250. (Laughter)

  251. But you get an idea
    of what we're up against,

  252. and why it's now up to us cryptographers
  253. to really step it up.
  254. And we have to do it fast,
  255. because quantum computers,
  256. they already exist in labs
    all over the world.
  257. Fortunately, at this minute,

  258. they only exist
    at a relatively small scale,
  259. still too small to break
    our much larger cryptographic keys.
  260. But we might not be safe for long.
  261. Some folks believe that secret
    government agencies
  262. have already built a big enough one,
  263. and they just haven't told anyone yet.
  264. Some pundits say
    they're more like 10 years off.
  265. Some people say it's more like 30.
  266. You might think that
    if quantum computers are 10 years away,
  267. surely that's enough time
    for us cryptographers to figure it out
  268. and to secure the internet in time.
  269. But unfortunately, it's not that easy.

  270. Even if we ignore
    the many years that it takes
  271. to standardize and deploy and then
    roll out new encryption technology,
  272. in some ways we may already be too late.
  273. Smart digital criminals
    and government agencies
  274. may already be storing
    our most sensitive encrypted data
  275. in anticipation for
    the quantum future ahead.
  276. The messages of foreign leaders,
  277. of war generals
  278. or of individuals who question power,
  279. they're encrypted for now.
  280. But as soon as the day comes
  281. that someone gets their hands
    on a quantum computer,
  282. they can retroactively break
    anything from the past.
  283. In certain government
    and financial sectors
  284. or in military organizations,
  285. sensitive data has got to remain
    classified for 25 years.
  286. So if a quantum computer
    really will exist in 10 years,
  287. then these guys are already
    15 years too late
  288. to quantum-proof their encryption.
  289. So while many scientists around the world

  290. are racing to try to build
    a quantum computer,
  291. us cryptographers are urgently
    looking to reinvent encryption
  292. to protect us long before that day comes.
  293. We're looking for new,
    hard mathematical problems.
  294. We're looking for problems that,
    just like factorization,
  295. can be used on our smartphones
    and on our laptops today.
  296. But unlike factorization,
    we need these problems to be so hard
  297. that they're even unbreakable
    with a quantum computer.
  298. In recent years, we've been digging around
    a much wider realm of mathematics

  299. to look for such problems.
  300. We've been looking at numbers and objects
  301. that are far more exotic
    and far more abstract
  302. than the ones that you and I are used to,
  303. like the ones on our calculators.
  304. And we believe we've found
    some geometric problems
  305. that just might do the trick.
  306. Now, unlike those two-
    and three-dimensional geometric problems
  307. that we used to have to try to solve
    with pen and graph paper in high school,
  308. most of these problems are defined
    in well over 500 dimensions.
  309. So not only are they a little hard
    to depict and solve on graph paper,
  310. but we believe they're even
    out of the reach of a quantum computer.
  311. So though it's early days,
  312. it's here that we are putting our hope
    as we try to secure our digital world
  313. moving into its quantum future.
  314. Just like all of the other scientists,

  315. we cryptographers are tremendously excited
  316. at the potential of living in a world
    alongside quantum computers.
  317. They could be such a force for good.
  318. But no matter what
    technological future we live in,
  319. our secrets will always be
    a part of our humanity.
  320. And that is worth protecting.
  321. Thanks.

  322. (Applause)