Injection

A injection is a function f:X→Y such that for each y∈Y there is at most one x∈X such that f(x)=y. Another way of stating this is that if x≠y then f(x)≠f(y).

Example

The function f(x)=x is an injection. The function f(x)=x2 is not an injection.

References

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