Editing Whirlpool (hash function) (section)

== Internal structure ==
The Whirlpool hash function is a [[Merkle–Damgård construction]] based on an [[Advanced Encryption Standard|AES]]-like [[block cipher]] W in [[One-way compression function#Miyaguchi–Preneel|Miyaguchi–Preneel]] mode.<ref name="whirlpoolpg" /> 

The [[block cipher]] W consists of an 8×8 state matrix <math>S</math> of bytes, for a total of 512 bits.

The encryption process consists of updating the state with four round functions over 10 rounds. The four round functions are SubBytes (SB), ShiftColumns (SC), MixRows (MR) and AddRoundKey (AK). During each round the new state is computed as
<math>S=AK \circ MR \circ SC \circ SB(S) </math>.

=== SubBytes ===
The '''SubBytes''' operation applies a non-linear permutation (the S-box) to each byte of the state independently. The 8-bit S-box is composed of 3 smaller 4-bit S-boxes.

=== ShiftColumns ===
The '''ShiftColumns''' operation cyclically shifts each byte in each column of the state. Column ''j'' has its bytes shifted downwards by ''j'' positions.

=== MixRows ===
The '''MixRows''' operation is a right-multiplication of each row by an 8×8 matrix over <math>GF({2^8})</math>. The matrix is chosen such that the [[branch number]] (an important property when looking at resistance to [[differential cryptanalysis]]) is 9, which is maximal.

=== AddRoundKey ===
The '''AddRoundKey''' operation uses bitwise [[Exclusive or|xor]] to add a key calculated by the key schedule to the current state. The key schedule is identical to the encryption itself, except the AddRoundKey function is replaced by an '''AddRoundConstant''' function that adds a predetermined constant in each round.