Permutation box

In cryptography, a permutation box (or P-box) is a method of bit-shuffling used to permute or transpose bits (rearrange or swap the order of bits) across S-boxes inputs, maintaining diffusion while transposing.

In block ciphers, the S-boxes and P-Boxes are used to make the relation between the plaintext and the ciphertext difficult to understand (see Shannon's property of diffusion).

Permutation Box Media

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  An example of a 64-bit "expansion" P-box which spreads the input S-boxes to as many output S-boxes as possible.

Related pages

• S-box
• Substitution cipher