Editing Serpent (cipher) (section)

== S-boxes ==
The Serpent s-boxes are 4-bit [[permutation]]s, and subject to the following properties:

* a 1-bit input difference will never lead to a 1-bit output difference, a differential characteristic has a probability of 1:4 or less.<ref name="algeb-2009" />
* linear characteristics have a probability between 1:2 and 1:4, linear relationship between input and output bits has a probability between 1:2 and 1:8.<ref name="algeb-2009" />
* the nonlinear order of the output bits as function of the input bits is 3. However there have been output bits found which in function of the input bits have an order of only 2.<ref name="algeb-2009" />

The Serpent s-boxes have been constructed based on the 32 rows of the [[Data Encryption Standard|DES]] s-boxes. These were transformed by swapping entries, resulting arrays with desired properties were stored as the Serpent s-boxes. This process was repeated until a total of 8 s-boxes were found. The following key was used in this process: <code>"sboxesforserpent"</code>.<ref name=":0" />