A surjection is a function `f:X→Y`

such that
for each `y∈Y`

there is at least one `x∈X`

such that `f(x)=y`

.

The function `f(x)=x`

is a surjection.

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

Copyright © 2014 Barry Watson. All rights reserved.