code: private String hash(byte[] password, byte[] salt) {
  		if (salt.length > 0) { // we can salt
  			byte[] message = new byte[salt.length + password.length];
  			System.arraycopy(salt, 0, message, 0, salt.length);
  			System.arraycopy(password, 0, message, salt.length, password.length);
  			return STR.joinArgs(SEPARATOR, Hex.encode(salt), Hex.encode(md.digest(message)));
  		}
  		return Hex.encode(md.digest(password));
  	}
docs: /* hashing