Unreported exception java.lang.Exception; must be caught or declared to be thrown

public static byte[] m16h(byte[] m) throws Exception

The signature of your method indicates that an Exception is susceptible of being thrown.

This means that the exception either :

1. Must be handled by the callertry { System.out.println(xor(m16h(add(xor(xor(m16h(add(k1, m16h(add(k2, m16h(k3))))), k3), k2), k1)), k3)); } catch (Exception e) { e.printStackTrace(); }
2. Must be rethrowed by the callerpublic static void main(String[] args) throws Exception