From d9af7a8f8a76bdf78d0056032d0e1d92d1e7f11e Mon Sep 17 00:00:00 2001
From: Ben Adams <thundercat@illyriad.co.uk>
Date: Sat, 1 Nov 2025 16:17:11 +0000
Subject: [PATCH] Optimize Ripemd

---
 .../Nethermind.Core.Test/RipemdTests.cs       |  2 +-
 src/Nethermind/Nethermind.Crypto/Ripemd.cs    | 32 +++++++++++--------
 .../Ripemd160Precompile.cs                    |  2 +-
 3 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/src/Nethermind/Nethermind.Core.Test/RipemdTests.cs b/src/Nethermind/Nethermind.Core.Test/RipemdTests.cs
index 88403a11e132..b7c4e8115218 100644
--- a/src/Nethermind/Nethermind.Core.Test/RipemdTests.cs
+++ b/src/Nethermind/Nethermind.Core.Test/RipemdTests.cs
@@ -9,7 +9,7 @@ namespace Nethermind.Core.Test
     [TestFixture]
     public class RipemdTests
     {
-        public const string RipemdOfEmptyString = "9c1185a5c5e9fc54612808977ee8f548b2258d31";
+        public const string RipemdOfEmptyString = "0000000000000000000000009c1185a5c5e9fc54612808977ee8f548b2258d31";
 
         [Test]
         public void Empty_byte_array()
diff --git a/src/Nethermind/Nethermind.Crypto/Ripemd.cs b/src/Nethermind/Nethermind.Crypto/Ripemd.cs
index fc02c2e524ef..8fc68db757e3 100644
--- a/src/Nethermind/Nethermind.Crypto/Ripemd.cs
+++ b/src/Nethermind/Nethermind.Crypto/Ripemd.cs
@@ -1,25 +1,29 @@
 // SPDX-FileCopyrightText: 2022 Demerzel Solutions Limited
 // SPDX-License-Identifier: LGPL-3.0-only
 
+using System;
 using Nethermind.Core.Extensions;
 using Org.BouncyCastle.Crypto.Digests;
 
-namespace Nethermind.Crypto
+namespace Nethermind.Crypto;
+
+public static class Ripemd
 {
-    public static class Ripemd
+    const int HashOutputLength = 32;
+
+    public static byte[] Compute(ReadOnlySpan<byte> input)
     {
-        public static byte[] Compute(byte[] input)
-        {
-            var digest = new RipeMD160Digest();
-            digest.BlockUpdate(input, 0, input.Length);
-            var result = new byte[digest.GetDigestSize()];
-            digest.DoFinal(result, 0);
-            return result;
-        }
+        RipeMD160Digest digest = new();
+        digest.BlockUpdate(input);
+        byte[] result = new byte[HashOutputLength];
+        int length = digest.GetDigestSize();
+        Span<byte> span = result.AsSpan(HashOutputLength - length, length);
+        digest.DoFinal(span);
+        return result;
+    }
 
-        public static string ComputeString(byte[] input)
-        {
-            return Compute(input).ToHexString(false);
-        }
+    public static string ComputeString(ReadOnlySpan<byte> input)
+    {
+        return Compute(input).ToHexString(false);
     }
 }
diff --git a/src/Nethermind/Nethermind.Evm.Precompiles/Ripemd160Precompile.cs b/src/Nethermind/Nethermind.Evm.Precompiles/Ripemd160Precompile.cs
index a4977a63c8c4..092a6689de57 100644
--- a/src/Nethermind/Nethermind.Evm.Precompiles/Ripemd160Precompile.cs
+++ b/src/Nethermind/Nethermind.Evm.Precompiles/Ripemd160Precompile.cs
@@ -38,6 +38,6 @@ public long DataGasCost(ReadOnlyMemory<byte> inputData, IReleaseSpec releaseSpec
     {
         Metrics.Ripemd160Precompile++;
 
-        return (Ripemd.Compute(inputData.ToArray()).PadLeft(32), true);
+        return (Ripemd.Compute(inputData.Span), true);
     }
 }