[YAYERKA]

In a cryptographic context;

>1.12 Definition

>A function f from a set X to a set Y is called a one-way function if f(x) is “easy” to compute for all x \in X but for “essentially all” elements y \in Im(f) it is “computationally infeasible” to find any x \in X such that f(x) = y. [0]

>1.16 Definition

>A trapdoor one-way function is a one-way function f : X -> Y with the additional property that given some extra information (called the trapdoor information) it becomes feasible to find for any given y \in Im(f), an x \in X such that f(x) = y. [0]

[0]; Menezes, A.; Oorschot, P. van; Vanstone, S. (2001). Handbook of Applied Cryptography (5th ed.). CRC Press.