From 77a2fc6100b27c83de99fe13715a259e88f8fa2d Mon Sep 17 00:00:00 2001
From: wborgeaud <williamborgeaud@gmail.com>
Date: Wed, 29 Dec 2021 16:58:31 +0100
Subject: [PATCH] Comment for KeccakPermutation

---
 plonky2/src/hash/keccak.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/plonky2/src/hash/keccak.rs b/plonky2/src/hash/keccak.rs
index 23166954..7bb2f133 100644
--- a/plonky2/src/hash/keccak.rs
+++ b/plonky2/src/hash/keccak.rs
@@ -6,6 +6,8 @@ use crate::plonk::config::Hasher;
 use crate::util::serialization::Buffer;
 
 /// Keccak-256 permutation used in the challenger.
+/// A state `input: [F; 12]` is sent to the field representation of `H(input) || H(H(input)) || H(H(H(input)))`
+/// where `H` is the Keccak-256 hash.
 pub struct KeccakPermutation;
 impl<F: RichField> PlonkyPermutation<F> for KeccakPermutation {
     fn permute(input: [F; SPONGE_WIDTH]) -> [F; SPONGE_WIDTH] {