Permutation box
Appearance
This article needs additional citations for verification. (March 2009) |
In cryptography, a permutation box (or P-box) is a method of bit-shuffling used to permute or transpose bits across inputs, retaining diffusion while transposing.[1]
In block ciphers, the S-boxes and P-boxes are used to make the relation between the key and the cyphertext as well as the plaintext and the ciphertext difficult to understand (see Shannon's propertyies of diffusion and confusion). 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.
See also
[edit]References
[edit]- ^ Computer Science and Engineering. Cryptography 2007 (PDF). Chalmers University of Technology.