public static BigInteger randomExponent(){
  SecureRandom sr=new SecureRandom();
  byte[] sb=new byte[MOD_LEN_BYTES];
  sr.nextBytes(sb);
  return new BigInteger(1,sb);
}

public static BigInteger randomExponent ( ) { SecureRandom sr = new SecureRandom ( ) ; byte [ ] sb = new byte [ MOD_LEN_BYTES ] ; sr . nextBytes ( sb ) ; return new BigInteger ( 1 , sb ) ; }
generate a random exponent
