Alice has a list of secret numbers. Alice wants to give Bob the opportunity to choose one of her secret numbers, and then Alice has to share that specific secret number, but in such a way that Alice can’t know which secret number Bob got to know. Is this known to be possible?

  • $\begingroup$ Is Bob honest? I.e., does it follow the provided protocol or can he deviate from the protocol in order to gain more information? $\endgroup$
    – Steven
    Commented Jul 25, 2021 at 12:18
  • $\begingroup$ Preferably Alice and Bob don’t need to rely on any form of trust. So Alice and Bob need to be able to prove after the fact that they followed the protocol. $\endgroup$ Commented Jul 25, 2021 at 12:20

1 Answer 1


This is known as the oblivious transfer problem. You can find about it online if you are looking for zero-knowledge interactive proofs for it.

  • 1
    $\begingroup$ Very cool! Thanks for the reference. $\endgroup$
    – Steven
    Commented Jul 25, 2021 at 13:07
  • 1
    $\begingroup$ Did you already know this, because I find it quite difficult to find stuff like this and had a hard time preventing search engines from misinterpreting my queries $\endgroup$ Commented Jul 25, 2021 at 13:29
  • $\begingroup$ @SmileyCraft yes, I learned about it in a cryptography course $\endgroup$
    – nir shahar
    Commented Jul 25, 2021 at 13:47

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