Permutation

A permutation of a set M is a bijection f:M→M. This is commonly used in a cipher to achieve diffusion.

Example

Consider the set M={1, 2, 3}. The function f(x)=x is a permutation. The function f={(1,3), (2,1), (3,2)} is also a permutation. The function f={(1,2), (2,3), (3,1)} is the inverse permutation of the previous permutation.

References

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