Thanks for this. I was unclear on this point. So looking at the discrete log pro... | Hacker News

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markc on May 18, 2015 | parent | context | favorite | on: Elliptic Curve Cryptography: a gentle introduction

Thanks for this. I was unclear on this point. So looking at the discrete log problem vs a trapdoor function:

    Discrete log: for f(x) = y
     - Easy: given f and x find y.
     - Hard: given f and y find x.

    Trapdoor: for f(x) = y
     - Easy: given f and y find x, given a secret, e.g. (p-1)(q-1) in RSA.
     - Hard: given f and y find x, without possesion of the secret.

Is that accurate, or have I misstated the essential difference somehow?

agwa on May 18, 2015 [–]

Yes, that's essentially the difference between a one-way function and a trapdoor function.

I'm sure you knew this already, but for completeness, another property of the trapdoor function is:

  - Easy: given f and x find y.

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