Permutation box

 ( Symmetric-key Cryptography ) 

In cryptography, a permutation box (or P-box) is a Methodology of bit-shuffling used to Permutation or transpose bits across Substitution box inputs, creating diffusion while transposing.

In based on substitution-permutation network, the P-boxes, together with the "substitution" are used to make the relation between the plaintext and the ciphertext difficult to understand (see Shannon's Confusion and diffusion). P-boxes are typically classified as compression, expansion, and straight, depending on whether the number of output bits is less than, greater than, or equal to the number of input bits, respectively. Only straight P-boxes are invertible.

• Boolean function
• Nothing-up-my-sleeve number
• Substitution cipher