Block Cipher
After a little googling I found this
Block Cipher Example:
For example, suppose the permutation was
XJEIOLUBGCDWZA YTFPSKMNQRHV
This could be made into a 3x3x3 array:
X I U C Z Y P M R
J O B D A T S N H
E L G W F K Q V
and the indices easily read off as row, column, layer (each indexed 0,1 2), so that T for example corresponds to (1,2,1).