Author: nextgens
Date: 2007-06-21 09:26:28 +0000 (Thu, 21 Jun 2007)
New Revision: 13677
Modified:
trunk/freenet/src/freenet/node/FNPPacketMangler.java
trunk/freenet/src/freenet/node/Node.java
Log:
Implement 1445: Use a mersenne twister or something for packet padding, not
Yarrow
Both the padding length and the padding itself are generated from MT... MT is
seeded once for all at node's startup; it should be enough for our purpose as
the period is 2^19937 - 1 (analysis of the randomness probably costy enough).
Modified: trunk/freenet/src/freenet/node/FNPPacketMangler.java
===================================================================
--- trunk/freenet/src/freenet/node/FNPPacketMangler.java 2007-06-20
23:09:21 UTC (rev 13676)
+++ trunk/freenet/src/freenet/node/FNPPacketMangler.java 2007-06-21
09:26:28 UTC (rev 13677)
@@ -438,7 +438,7 @@
BlockCipher cipher = pn.outgoingSetupCipher;
if(logMINOR) Logger.minor(this, "Outgoing cipher:
"+HexUtil.bytesToHex(pn.outgoingSetupKey));
PCFBMode pcfb = PCFBMode.create(cipher);
- int paddingLength = node.random.nextInt(100);
+ int paddingLength = node.fastWeakRandom.nextInt(100);
byte[] iv = new byte[pcfb.lengthIV()];
node.random.nextBytes(iv);
byte[] hash = SHA256.digest(output);
@@ -454,8 +454,7 @@
pcfb.blockEncipher(output, 0, output.length);
System.arraycopy(output, 0, data, hash.length+iv.length+2,
output.length);
byte[] random = new byte[paddingLength];
- // FIXME don't use node.random
- node.random.nextBytes(random);
+ node.fastWeakRandom.nextBytes(random);
System.arraycopy(random, 0, data,
hash.length+iv.length+2+output.length, random.length);
try {
sendPacket(data, replyTo, pn, 0);
@@ -1254,11 +1253,11 @@
// Ideally we'd mimic the size profile - and the session bytes! - of a
common protocol.
int paddedLen = ((packetLength + 63) / 64) * 64;
- paddedLen += node.random.nextInt(64);
+ paddedLen += node.fastWeakRandom.nextInt(64);
if(packetLength <= 1280 && paddedLen > 1280) paddedLen = 1280;
byte[] padding = new byte[paddedLen - packetLength];
- node.random.nextBytes(padding);
+ node.fastWeakRandom.nextBytes(padding);
packetLength = paddedLen;
Modified: trunk/freenet/src/freenet/node/Node.java
===================================================================
--- trunk/freenet/src/freenet/node/Node.java 2007-06-20 23:09:21 UTC (rev
13676)
+++ trunk/freenet/src/freenet/node/Node.java 2007-06-21 09:26:28 UTC (rev
13677)
@@ -28,10 +28,12 @@
import java.util.Iterator;
import java.util.Locale;
import java.util.MissingResourceException;
+import java.util.Random;
import java.util.zip.DeflaterOutputStream;
import net.i2p.util.NativeBigInteger;
+import org.spaceroots.mantissa.random.MersenneTwister;
import org.tanukisoftware.wrapper.WrapperManager;
import com.sleepycat.je.DatabaseException;
@@ -318,7 +320,6 @@
private DSAPrivateKey myPrivKey;
/** My public key */
private DSAPublicKey myPubKey;
-
/** My ARK SSK private key */
InsertableClientSSK myARK;
/** My ARK sequence number */
@@ -370,6 +371,8 @@
final File extraPeerDataDir;
/** Strong RNG */
public final RandomSource random;
+ /** Weak but fast RNG */
+ public final Random fastWeakRandom;
final UdpSocketManager usm;
final FNPPacketMangler packetMangler;
final DNSRequester dnsr;
@@ -732,6 +735,8 @@
recentlyCompletedIDs = new LRUQueue();
this.config = config;
this.random = random;
+ // Seeding it with anything longer than an int is useless
+ this.fastWeakRandom = new MersenneTwister(random.nextInt());
cachedPubKeys = new LRUHashtable();
lm = new LocationManager(random);
