From ff608af82a72e1e6fdd3b299f3e0b1e3a9902d47 Mon Sep 17 00:00:00 2001
From: agureev <artguril@proton.me>
Date: Fri, 19 Jun 2026 20:07:51 +0400
Subject: [PATCH] feat: add a Risc0 backend

Defaults to software keccak on unoptimized rounds
---
 keccak/src/backends/risc0.rs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 keccak/src/backends/risc0.rs

diff --git a/keccak/src/backends/risc0.rs b/keccak/src/backends/risc0.rs
new file mode 100644
index 0000000..1a0414b
--- /dev/null
+++ b/keccak/src/backends/risc0.rs
@@ -0,0 +1,23 @@
+use crate::consts::F1600_ROUNDS;
+use crate::types::{Fn1600, State1600};
+#[cfg(feature = "parallel")]
+use hybrid_array::typenum::U1;
+
+pub(crate) struct Backend;
+
+impl super::Backend for Backend {
+    #[cfg(feature = "parallel")]
+    type ParSize1600 = U1;
+
+    #[inline]
+    fn get_p1600<const ROUNDS: usize>() -> Fn1600 {
+        if ROUNDS == F1600_ROUNDS {
+            return risc0_p1600;
+        }
+        super::soft::keccak_p::<u64, ROUNDS>
+    }
+}
+
+fn risc0_p1600(state: &mut State1600) {
+    risc0_zkvm::guest::env::risc0_keccak_update(state);
+}