Added 'toPublic()' methods to PrivateKey and SigningPrivateKey, such

that these return PublicKey and SigningPublicKey objects, respectively.

core/java/src/net/i2p/crypto/KeyGenerator.java

@@ -76,6 +76,20 @@ public class KeyGenerator {
         return keys;
     }
 
+    /** Convert a PrivateKey to its corresponding PublicKey
+     * @param a PrivateKey object
+     * @return the corresponding PublicKey object
+     * @author aum
+     */
+    public static PublicKey getPublicKey(PrivateKey priv) {
+        BigInteger a = new NativeBigInteger(priv.toByteArray());
+        BigInteger aalpha = CryptoConstants.elgg.modPow(a, CryptoConstants.elgp);
+        PublicKey pub = new PublicKey();
+        byte [] pubBytes = aalpha.toByteArray();
+        pub.setData(padBuffer(pubBytes, PublicKey.KEYSIZE_BYTES));
+        return pub;
+    }
+
     /** Generate a pair of DSA keys, where index 0 is a SigningPublicKey, and
      * index 1 is a SigningPrivateKey
      * @return pair of keys
@@ -100,6 +114,20 @@ public class KeyGenerator {
         return keys;
     }
 
+    /** Convert a SigningPrivateKey to a SigningPublicKey
+     * @param a SigningPrivateKey object
+     * @return a SigningPublicKey object
+     * @author aum
+     */
+    public static SigningPublicKey getSigningPublicKey(SigningPrivateKey priv) {
+        BigInteger x = new NativeBigInteger(priv.toByteArray());
+        BigInteger y = CryptoConstants.dsag.modPow(x, CryptoConstants.dsap);
+        SigningPublicKey pub = new SigningPublicKey();
+        byte [] pubBytes = padBuffer(y.toByteArray(), SigningPublicKey.KEYSIZE_BYTES);
+        pub.setData(pubBytes);
+        return pub;
+    }
+
     /**
      * Pad the buffer w/ leading 0s or trim off leading bits so the result is the
      * given length.  

core/java/src/net/i2p/data/PrivateKey.java

@@ -14,6 +14,7 @@ import java.io.InputStream;
 import java.io.OutputStream;
 
 import net.i2p.util.Log;
+import net.i2p.crypto.KeyGenerator;
 
 /**
  * Defines the PrivateKey as defined by the I2P data structure spec.
@@ -77,4 +78,14 @@ public class PrivateKey extends DataStructureImpl {
         buf.append("]");
         return buf.toString();
     }
+
+    /** derives a new PublicKey object derived from the secret contents
+     * of this PrivateKey
+     * @return a PublicKey object
+     * @author aum
+     */
+    public PublicKey toPublic() {
+        return KeyGenerator.getPublicKey(this);
+    }
+
 }

core/java/src/net/i2p/data/PublicKey.java

@@ -76,4 +76,5 @@ public class PublicKey extends DataStructureImpl {
         buf.append("]");
         return buf.toString();
     }
+
 }

core/java/src/net/i2p/data/SigningPrivateKey.java

@@ -14,6 +14,7 @@ import java.io.InputStream;
 import java.io.OutputStream;
 
 import net.i2p.util.Log;
+import net.i2p.crypto.KeyGenerator;
 
 /**
  * Defines the SigningPrivateKey as defined by the I2P data structure spec.
@@ -76,4 +77,12 @@ public class SigningPrivateKey extends DataStructureImpl {
         buf.append("]");
         return buf.toString();
     }
+
+    /** converts this signing private key to its public equivalent
+     * @return a SigningPublicKey object derived from this private key
+     * @author aum
+     */
+    public SigningPublicKey toPublic() {
+        return KeyGenerator.getSigningPublicKey(this);
+    }
 }