Pollard's rho algorithm for logarithms

Pollard's rho algorithm for logarithms is an algorithm introduced by John Pollard in 1978 to solve the discrete logarithm problem, analogous to Pollard's rho algorithm to solve the integer factorization problem.

The goal is to compute ${\displaystyle \gamma }$ such that ${\displaystyle \alpha ^{\gamma }=\beta }$, where ${\displaystyle \beta }$ belongs to a cyclic group ${\displaystyle G}$ generated by ${\displaystyle \alpha }$. The algorithm computes integers ${\displaystyle a}$, ${\displaystyle b}$, ${\displaystyle A}$, and ${\displaystyle B}$ such that ${\displaystyle \alpha ^{a}\beta ^{b}=\alpha ^{A}\beta ^{B}}$. If the underlying group is cyclic of order ${\displaystyle n}$, ${\displaystyle \gamma }$ is one of the solutions of the equation ${\displaystyle (B-b)\gamma =(a-A){\pmod {n}}}$.

...
Wikipedia