Just to clarify: the cryptocurrency idea mentioned here is still state-backed; the prime advantages of a digital currency are in rapid transaction and in giving the state Bank more direct control over the money in circulation.

At present, the bank can choose not print more money (leading to deflation), or print money to slowly increase the amount of money in circulation (leading to controlled inflation, reducing the value of money in private wallets and encouraging spending behavior).

Digital currency will allow the state to simply dirrctly reduce the value of money (negative interest) across all private wallets to encourage spending behavior.

It is a very interesting approach that I think challenges our intuitions about currency, and will take some time to get used to.

I'm still usually using cash when paying for stuff. I don't use plastic, because I value privacy. However, I would be more than happy to ditch cash if I could use a cryptocurrency, that had good privacy, instead.

What does it even mean to have a negative interest rate?

That if you put money somewhere that has negative interest, you have to pay a percentage for it, instead of receiving it. (=you pay for storing money, instead of getting a reward for it)

Ah ok, so the purpose is to cause you to invest or spend it.