Keccak Permutation Référence
Detailed référence pour le Keccak-f[1600] permutation underlying SHA-3 et related primitives.
Round Steps
The Keccak-f permutation applies 24 rounds, each consisting of five steps: theta, rho, pi, chi, iota. Theta mixes columns via parity, rho rotates lanes by fixed offsets, pi permutes lane positions, chi adds nonlinearity via AND, and iota adds a round constant. The state is a 5x5 array of 64-bit lanes totaling 1600 bits. Only chi provides nonlinearity; the other steps are linear or affine.
- theta
- Column parity mixing
- rho/pi
- Lane rotation and permutation
- chi
- AND-based nonlinearity
linearlinearonly nonlinear stepSecurity Properties
The Keccak permutation is designed to resist differential and linear cryptanalysis with high algebraic degree. The sponge construction's capacity parameter directly controls security bounds. The 24-round version has a large security margin; reduced-round attacks reach only a few rounds. The permutation also serves as a PRP and underlies keyed sponge modes for encryption and authentication.
- algebraic degree
- High, grows per round
- margin
- Large at 24 rounds
- keyed sponge
- Encryption/MAC mode
resists algebraic attacksattacks on few roundsduplex construction