The idea of paper money being banned is ludicrous, I mean maybe in the distant future sure but I haven't seen any proposals whatsoever for how a digital currency could ever work in an offline setting. Paper money works whether an internet or phone connection is available and even when there is no electricity. If we had a bitcoin based digital currency what will happen when the internet goes down, will transactions be unavailable until it is working again?
Think about disaster hit areas, without paper money transactions would be impossible in all but an old fashioned barter setting.
The Internet has become a necessity to us. If the Internet goes down, it would be one of the first things your government will fix. Most part of the economy depends on the Internet because they need to communicate to other people. You don't have to worry about the things that only have a small chance of happening.
In addition to this, if disaster hits your country so hard that even the telephone wires got destroyed, do you really think people would just carry on with their lives and buy and sell things as if nothing happened? Paper money will just as useless as any other currencies at that point. People will choose to fix everything else before they get back to their feet.