It isn't just IE that is a problem. The encryption scheme developed by the government is largely broken (due in no small part to IE and ActiveX vulnerabilities). South Korean banks and other organisations are losing money due to fraud and blackhat activity but there is next to nothing they can do about it. It's really a huge mess. That and the government's encryption app is closed source and not peer reviewed.

As always, the cause is that you are never smart enough to roll your own encryption standard. Any time someone asks you to roll your own encryption pinch yourself and smash your head on the desk, if you still want to code it smash your head again.