The fact crypto is a digital currency it's totally dependable on electricity.
Also cash is becoming less and less common in favor of electronic bank accounts.
Now that there is talk about EMP Bombs, how will cryptocurrency be protected?
for those who don't know what EMP is. EMP's are simply electromagnetic pulse which can affect electronic devices but this only happens if the device is close enough to the source of EMP to be affected.
The largest EMP source can be produced by a nuclear explosions and even the most powerful nuclear bomb won't be able to wipe out all data centers, infrastructures and servers scatter across the world and the produced EMP is not enough to affect all electronic device in the world.
As for the question of how will cryptocurrency be protected? As long as the servers who hold the data of the blockhain is never directly hit by the EMP the crytocurrency is safe but there will be delays in the transaction and lost of coins as for the network traffic will surely be affected by the EMP attack is there is one.