How to Toss a Coin Over the Phone


Wednesday, April 18th at 5 pm in PHSC 1105

our own Dr. Ravi Shankar will be talking in the Math Club.  He answer the puzzling problem of telling someone something without telling them and related conundrums:

Your favorite uncle Mo who lived in Alaska has recently gifted you his zamboni. But he left it to you and his other favorite niece, Eva, who lives in Arizona. You give Eva a call and neither of you wants to share the zamboni. You decide to flip a coin for it. So Eva flips and you call, “Heads!” and she says, “Oops, sorry, no. You lose.” To which you reply, “I don’t believe you!” An argument ensues until you realize you went to a math club talk at OU, where you were shown how to flip a coin over the phone and both be reasonably sure that the other person could not have cheated.

In this talk we will explore how to solve this problem and other similar “authentication” and “signature” problems (how do you convince a bank teller on the phone that you know the secret pin number for your account without actually revealing the pin number?)

— Dr. Shankar’s abstract

There's more than one way to find out what somebody knows! 🙂

As always, Free Pizza!

P.S.  Come and quiz Dr. Shankar on Weierstrass gap sequences!


2 thoughts on “How to Toss a Coin Over the Phone

  1. I just wanted to mention that this week’s lecture by Dr. Shankar was the best one of all Math Club lectures this semester. The topic was very interesting and Dr. Shankar’s presentation was very clear and engaging. Please have him lecture next semester as well. Thanks!

    • Billy,

      We agree! Thanks for the comment and we’ll let Dr. Shankar know that he needs to do an encore!

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