From b661f6a2db6b4358dfe02cd40fd531d801cdd1e0 Mon Sep 17 00:00:00 2001
From: Bert Massop <bert.massop@gmail.com>
Date: Mon, 12 May 2025 22:50:35 +0200
Subject: [PATCH] Do not synchronize on global variable in
 CryptoKey.fingerprint

Unlikely to lead to any real-world performance gains as this code is
seldom used, but more the reason to just get a fresh digest when needed.
---
 src/freenet/crypt/CryptoKey.java    | 21 +++++----------------
 src/freenet/crypt/DSAPublicKey.java | 11 ++++++-----
 2 files changed, 11 insertions(+), 21 deletions(-)

diff --git a/src/freenet/crypt/CryptoKey.java b/src/freenet/crypt/CryptoKey.java
index 03bf306c5f..272a4787d7 100644
--- a/src/freenet/crypt/CryptoKey.java
+++ b/src/freenet/crypt/CryptoKey.java
@@ -10,7 +10,6 @@
 import java.lang.reflect.Method;
 import java.math.BigInteger;
 import java.security.MessageDigest;
-import java.security.NoSuchAlgorithmException;
 
 import freenet.support.HexUtil;
 import freenet.support.Logger;
@@ -18,15 +17,6 @@
 public abstract class CryptoKey implements CryptoElement, Serializable {
 
     private static final long serialVersionUID = 1L;
-    protected static final MessageDigest shactx;
-	static {
-		try {
-			shactx = MessageDigest.getInstance("SHA1", Util.mdProviders.get("SHA1"));
-		} catch(NoSuchAlgorithmException e) {
-			// impossible
-			throw new Error(e);
-		}
-	}
 
 	CryptoKey() {
 	}
@@ -57,13 +47,12 @@ public static CryptoKey read(InputStream i) throws IOException, CryptFormatExcep
 	public abstract byte[] asBytes();
 
 	protected byte[] fingerprint(BigInteger[] quantities) {
-		synchronized (shactx) {
-			for (BigInteger quantity: quantities) {
-				byte[] mpi = Util.MPIbytes(quantity);
-				shactx.update(mpi, 0, mpi.length);
-			}
-			return shactx.digest();
+		MessageDigest shactx = HashType.SHA1.get();
+		for (BigInteger quantity: quantities) {
+			byte[] mpi = Util.MPIbytes(quantity);
+			shactx.update(mpi, 0, mpi.length);
 		}
+		return shactx.digest();
 	}
 
 	public String verboseToString() {
diff --git a/src/freenet/crypt/DSAPublicKey.java b/src/freenet/crypt/DSAPublicKey.java
index ec751a430d..c978c6fb82 100644
--- a/src/freenet/crypt/DSAPublicKey.java
+++ b/src/freenet/crypt/DSAPublicKey.java
@@ -22,7 +22,7 @@ public class DSAPublicKey extends CryptoKey implements StorableBlock {
 	public static final int HASH_LENGTH = 32;
 	/** Null means use Global.DSAgroupBigA. This makes persistence simpler. */
 	private final DSAGroup group;
-	private byte[] fingerprint = null;
+	private volatile byte[] fingerprint;
 	
 	public DSAPublicKey(DSAGroup g, BigInteger y) {
 		if(y.signum() != 1)
@@ -151,11 +151,12 @@ public byte[] asPaddedBytes() {
 
 	@Override
 	public byte[] fingerprint() {
-		synchronized(this) {
-			if(fingerprint == null)
-				fingerprint = fingerprint(new BigInteger[]{y});
-			return fingerprint;
+		byte[] fingerprint = this.fingerprint;
+		if (fingerprint == null) {
+			fingerprint = fingerprint(new BigInteger[]{y});
+			this.fingerprint = fingerprint;
 		}
+		return fingerprint;
 	}
 
 	public boolean equals(DSAPublicKey o) {