When you have a fully digital system you have no weapon to defend yourself if someone turns it off, he says.

If Putin invades Gotland [Sweden’s largest island] it will be enough for him to turn off the payments system. No other country would even think about taking these sorts of risks, they would demand some sort of analogue system.Being cash-free puts us at risk of attack: Swedes turn against cashlessness

First of all, if Putin were to invade Sweden, not being to be able to pay for things would be the least of our problems. Secondly, to hack our digital systems, he surely wouldn't need to invade Sweden first. Thirdly, if he were to hack us, I'm pretty sure he would take down electricity, water supply and other crucial things before going after our payments.