A trapdoor one-way function `f:X→Y`

is a one-way function
where it becomes easy to compute `x∈X`

for a given `y∈Y`

such that `f(x)=y`

when the trapdoor information is known.
Essentially, the "one-wayness" of the function depends on not knowing the trapdoor information.

A. Menzes, P. van Oorschot, and S. Vanstone, *Handbook of Applied Cryptography.* CRC Press, 1996.

Copyright © 2014 Barry Watson. All rights reserved.