# Tag Info

6

It is equivalent to the computational Diffie-Hellman problem; if you can one of the two problems, you can solve the other (with a polynomial number of queries to the oracle which solves the other). If you can solve the Diffie-Hellman problem, you can solve your problem: this can be seen by first noting that, with a Diffie-Hellman solver, given $g^b$, you ...

4

Not at all. It's very trivial: $$(g^{ab})^{b^{-1}}=g^a$$

3

The question as currently worded, and considering comments by its author, would boil down to: is it a hard problem finding $g^a\bmod p$, given large prime $p$ large integer $g$ less than $p$ that is a generator of $\mathbb Z_p$ [see note 1] prime $r$ less than $p$ knowledge that unknown $a$ is a positive integer less than $r$ positive integer $b$ less than ...

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