content: /*
      James Robson
      Public domain.
  */
  
  public class Curve25519Donna {
  
      final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
  
      public static String bytesToHex(byte[] bytes) {
          char[] hexChars = new char[bytes.length * 2];
          int v;
          for ( int j = 0; j < bytes.length; j++ ) {
              v = bytes[j] & 0xFF;
              hexChars[j * 2] = hexArray[v >>> 4];
              hexChars[j * 2 + 1] = hexArray[v & 0x0F];
          }
          return new String(hexChars);
      }
  
      public native byte[] curve25519Donna(byte[] a, byte[] b);
      public native byte[] makePrivate(byte[] secret);
      public native byte[] getPublic(byte[] privkey);
      public native byte[] makeSharedSecret(byte[] privkey, byte[] theirPubKey);
      public native void helowrld();
  
      // Uncomment if your Java is 32-bit:
      //static { System.loadLibrary("Curve25519Donna"); }
  
      // Otherwise, load this 64-bit .jnilib:
      static { System.loadLibrary("Curve25519Donna_64"); }
  
      /*
          To give the old tires a kick (OSX):
          java -cp `pwd` Curve25519Donna
      */
      public static void main (String[] args) {
  
          Curve25519Donna c = new Curve25519Donna();
  
          // These should be 32 bytes long
          byte[] user1Secret = "abcdefghijklmnopqrstuvwxyz123456".getBytes();
          byte[] user2Secret = "654321zyxwvutsrqponmlkjihgfedcba".getBytes();
  
  
          // You can use the curve function directly...
  
          //byte[] o = c.curve25519Donna(a, b);
          //System.out.println("o = " + bytesToHex(o));
  
  
          // ... but it's not really necessary. Just use the following
          // convenience methods:
  
          byte[] privKey = c.makePrivate(user1Secret);
          byte[] pubKey = c.getPublic(privKey);
  
          byte[] privKey2 = c.makePrivate(user2Secret);
          byte[] pubKey2 = c.getPublic(privKey2);
  
          System.out.println("'user1' privKey = " + bytesToHex(privKey));
          System.out.println("'user1' pubKey = " + bytesToHex(pubKey));
          System.out.println("===================================================");
  
          System.out.println("'user2' privKey = " + bytesToHex(privKey2));
          System.out.println("'user2' pubKey = " + bytesToHex(pubKey2));
          System.out.println("===================================================");
  
  
          byte[] ss1 = c.makeSharedSecret(privKey, pubKey2);
          System.out.println("'user1' computes shared secret: " + bytesToHex(ss1));
  
          byte[] ss2 = c.makeSharedSecret(privKey2, pubKey);
          System.out.println("'user2' computes shared secret: " + bytesToHex(ss2));
  
      }
  }
  