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← 01ps-08 One Time Pad

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Showing Revision 1 created 10/24/2012 by Amara Bot.

  1. [Narrator] The next question checks that you understand one-time pads.
  2. Alice and Bob have agreed on a perfectly random key
  3. and that Alice will send Bob the answer to the question, "Are you taking CS 387?"
  4. As either the single character Y or the single character N.
  5. This will be encoded using the string to bits procedure,
  6. which takes in a string and gives you a list of bits,
  7. and the results of string to bits Y is 1011001,
  8. and the route for N is 1001110.
  9. Mallory knows nothing about the key or the message,
  10. but she intercepts the transmission between Alice and Bob,
  11. and intercepts this sequence of bits,
  12. and Mallory wants to cause trouble between Alice and Bob.
  13. She wants to make Bob hear the opposite of what Alice sent
  14. so if Alice sent a Y, Mallory wants Bob to hear an N.
  15. If Alice sent an N, Mallory wants Bob to hear a Y.
  16. What should Mallory send instead of the original message that she intercepted,
  17. and your answer should be in the form of 7 bits, each of which is a 0 or a 1.
  18. Once you understand the answer to this,
  19. I want to encourage you to join an open discussion question, which is
  20. is there a way to solve this problem without using anything other than a one-time pad?
  21. Is there a way for Alice and Bob to communicate correctly the answer to this question
  22. and know that it can't be altered in transmission and still preserve all the privacy properties of a one-time pad?