Extracting Private Keys in Diffie Hellman I know that the security of Diffie Hellman Key Exchange depends upon the discrete logarithm problem, but is it possible to extract the private keys if we know more? Say that in addition to modulus ($q$), primitive root ($g$) and public keys of Alice and Bob ($g^a$ and $g^b$ respectively), if we knew the calculated key ($g^{ab}$) as well, will it be possible to extract individual keys of Alice and Bob ($a$ and $b$) without using a brute force method? I know it sounds silly and serves no practical purpose at all, but the question was bugging me.

Thanks,

Edit: Added $g$ and other variables for clarity.
This is as hard as computing the discrete logarithm: Assume you have an algorithm $\mathcal{A}$ that given $g^a$, $g^b$ and $g^{ab}$ efficiently computes $a$ and $b$ for uniform $a$ and $b$. You can use this algorithm to compute discrete logarithms as follows: Given $h = g^a$, choose a uniform $b$, compute $g^b$ and $h^b = g^{ab}$. Now give $g^a$, $g^b$ and $g^{ab}$ to $\mathcal{A}$ to obtain $a$, the discrete logarithm of $h$.