From 3d6ff7c8616be578273c7acf5fdd11068e852526 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Piotr=20Miko=C5=82ajczyk?= <piomiko41@gmail.com>
Date: Thu, 13 Nov 2025 15:17:10 +0100
Subject: [PATCH 1/2] Add keccak_wasm.go

---
 crypto/keccak.go       |  2 +-
 crypto/keccak_wasm.go  | 55 ++++++++++++++++++++++++++++++++++++++++++
 crypto/keccak_ziren.go |  2 +-
 3 files changed, 57 insertions(+), 2 deletions(-)
 create mode 100644 crypto/keccak_wasm.go

diff --git a/crypto/keccak.go b/crypto/keccak.go
index 0ad79a63c1..c31229e47e 100644
--- a/crypto/keccak.go
+++ b/crypto/keccak.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-//go:build !ziren
+//go:build !ziren && !wasm
 
 package crypto
 
diff --git a/crypto/keccak_wasm.go b/crypto/keccak_wasm.go
new file mode 100644
index 0000000000..1959d34c4d
--- /dev/null
+++ b/crypto/keccak_wasm.go
@@ -0,0 +1,55 @@
+// Copyright 2025, Offchain Labs, Inc.
+// For license information, see https://github.com/OffchainLabs/nitro/blob/master/LICENSE.md
+
+//go:build wasm && !ziren
+
+package crypto
+
+import (
+	"unsafe"
+
+	"github.com/ethereum/go-ethereum/common"
+	"golang.org/x/crypto/sha3"
+)
+
+// NewKeccakState creates a new KeccakState
+func NewKeccakState() KeccakState {
+	return sha3.NewLegacyKeccak256().(KeccakState)
+}
+
+// Keccak256 calculates and returns the Keccak256 hash of the input data.
+func Keccak256(data ...[]byte) []byte {
+	b := make([]byte, 32)
+	keccak256Digest(b, data...)
+	return b
+}
+
+// Keccak256Hash calculates and returns the Keccak256 hash of the input data,
+// converting it to an internal Hash data structure.
+func Keccak256Hash(data ...[]byte) (h common.Hash) {
+	keccak256Digest(h[:], data...)
+	return h
+}
+
+func keccak256Digest(out []byte, data ...[]byte) {
+	if len(out) != 32 {
+		panic("output buffer must be 32 bytes")
+	}
+
+	flattenedInput := make([]byte, 0)
+	for _, b := range data {
+		flattenedInput = append(flattenedInput, b...)
+	}
+
+	var inputPtr unsafe.Pointer
+	if len(flattenedInput) > 0 {
+		inputPtr = unsafe.Pointer(&flattenedInput[0])
+	} else {
+		inputPtr = unsafe.Pointer(nil)
+	}
+
+	outsourcedKeccak(inputPtr, uint32(len(flattenedInput)), unsafe.Pointer(&out[0]))
+}
+
+//go:wasmimport arbkeccak keccak256
+func outsourcedKeccak(inBuf unsafe.Pointer, inLen uint32, outBuf unsafe.Pointer)
diff --git a/crypto/keccak_ziren.go b/crypto/keccak_ziren.go
index 8e967c6dbf..67a9c17487 100644
--- a/crypto/keccak_ziren.go
+++ b/crypto/keccak_ziren.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-//go:build ziren
+//go:build ziren && !wasm
 
 package crypto
 

From 47225f94fba65b196a91fc1ccdf6e4850397f17b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Piotr=20Miko=C5=82ajczyk?= <piomiko41@gmail.com>
Date: Tue, 18 Nov 2025 13:55:37 +0100
Subject: [PATCH 2/2] minor code adjustment

---
 crypto/keccak_wasm.go | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/crypto/keccak_wasm.go b/crypto/keccak_wasm.go
index 1959d34c4d..e6e2c706c9 100644
--- a/crypto/keccak_wasm.go
+++ b/crypto/keccak_wasm.go
@@ -40,15 +40,14 @@ func keccak256Digest(out []byte, data ...[]byte) {
 	for _, b := range data {
 		flattenedInput = append(flattenedInput, b...)
 	}
+	inputLen := len(flattenedInput)
 
-	var inputPtr unsafe.Pointer
-	if len(flattenedInput) > 0 {
+	inputPtr := unsafe.Pointer(nil)
+	if inputLen > 0 {
 		inputPtr = unsafe.Pointer(&flattenedInput[0])
-	} else {
-		inputPtr = unsafe.Pointer(nil)
 	}
 
-	outsourcedKeccak(inputPtr, uint32(len(flattenedInput)), unsafe.Pointer(&out[0]))
+	outsourcedKeccak(inputPtr, uint32(inputLen), unsafe.Pointer(&out[0]))
 }
 
 //go:wasmimport arbkeccak keccak256