* Crypto: Don't use "short exponent" on faster platforms.

Rebuild router identity if key length doesn't match setting.
   This affects RI and LS encryption keys, and DH and YK.
   Faster = 64 bit with working jbigi, non-ARM, non-GNU (for now)
   Override default with crypto.elGamal.useLongKey=true/false
   LS key is built at client startup (Dest key unused)
   This will churn most of the RIs at the release.
 * SystemVersion: Add isARM()

router/java/src/net/i2p/router/RouterVersion.java

@@ -18,7 +18,7 @@ public class RouterVersion {
     /** deprecated */
     public final static String ID = "Monotone";
     public final static String VERSION = CoreVersion.VERSION;
-    public final static long BUILD = 23;
+    public final static long BUILD = 24;
 
     /** for example "-test" */
     public final static String EXTRA = "";

router/java/src/net/i2p/router/startup/LoadRouterInfoJob.java

@@ -14,6 +14,7 @@ import java.io.FileInputStream;
 import java.io.InputStream;
 import java.io.IOException;
 
+import net.i2p.crypto.KeyGenerator;
 import net.i2p.data.DataFormatException;
 import net.i2p.data.PrivateKey;
 import net.i2p.data.PublicKey;
@@ -91,6 +92,14 @@ public class LoadRouterInfoJob extends JobImpl {
                 fis2 = new BufferedInputStream(new FileInputStream(rkf));
                 PrivateKey privkey = new PrivateKey();
                 privkey.readBytes(fis2);
+                if (shouldRebuild(privkey)) {
+                    _us = null;
+                    rif.delete();
+                    rkf.delete();
+                    _infoExists = false;
+                    _keysExist = false;
+                    return;
+                }
                 SigningPrivateKey signingPrivKey = new SigningPrivateKey();
                 signingPrivKey.readBytes(fis2);
                 PublicKey pubkey = new PublicKey();
@@ -119,4 +128,29 @@ public class LoadRouterInfoJob extends JobImpl {
             if (fis2 != null) try { fis2.close(); } catch (IOException ioe) {}
         }
     }
+
+    /**
+     *  Does our RI private key length match the configuration?
+     *  If not, return true.
+     *  @since 0.9.8
+     */
+    private boolean shouldRebuild(PrivateKey privkey) {
+        byte[] pkd = privkey.getData();
+        boolean haslong = false;
+        for (int i = 0; i < 8; i++) {
+            if (pkd[i] != 0) {
+                haslong = true;
+                break;
+            }
+        }
+        boolean uselong = getContext().keyGenerator().useLongElGamalExponent();
+        // transition to a longer key (update to 0.9.8)
+        if (uselong && !haslong)
+            _log.logAlways(Log.WARN, "Rebuilding RouterInfo with longer key");
+        // transition to a shorter key, should be rare (copy files to different hardware,
+        // jbigi broke, user overrides in advanced config, ...)
+        if (!uselong && haslong)
+            _log.logAlways(Log.WARN, "Rebuilding RouterInfo with faster key");
+        return uselong != haslong;
+    }
 }

router/java/src/net/i2p/router/transport/crypto/DHSessionKeyBuilder.java

@@ -71,7 +71,7 @@ public class DHSessionKeyBuilder {
      * Others should get instances from PrecalcRunner.getBuilder()
      */
     DHSessionKeyBuilder() {
-        this(RandomSource.getInstance());
+        this(I2PAppContext.getGlobalContext());
     }
 
     /**
@@ -79,8 +79,8 @@ public class DHSessionKeyBuilder {
      * Only for internal use and unit tests.
      * Others should get instances from PrecalcRunner.getBuilder()
      */
-    DHSessionKeyBuilder(RandomSource random) {
-        _myPrivateValue = new NativeBigInteger(KeyGenerator.PUBKEY_EXPONENT_SIZE, random);
+    DHSessionKeyBuilder(I2PAppContext ctx) {
+        _myPrivateValue = new NativeBigInteger(ctx.keyGenerator().getElGamalExponentSize(), ctx.random());
         _myPublicValue = CryptoConstants.elgg.modPow(_myPrivateValue, CryptoConstants.elgp);
         _extraExchangedBytes = new ByteArray();
     }
@@ -547,7 +547,7 @@ public class DHSessionKeyBuilder {
 
         private DHSessionKeyBuilder precalc() {
             long start = System.currentTimeMillis();
-            DHSessionKeyBuilder builder = new DHSessionKeyBuilder(_context.random());
+            DHSessionKeyBuilder builder = new DHSessionKeyBuilder(_context);
             long end = System.currentTimeMillis();
             long diff = end - start;
             _context.statManager().addRateData("crypto.dhGeneratePublicTime", diff, diff);