I have a doubt with Proof of Stake. As I have watched some tutorial videos and websites, there is information that: with Proof of Stake, in order to make a double spending attack, a node has to own at least 51% stake of all the network.
Because with pure Proof of Stake, only a single miner can append a block at the same time. So what I wonder here is: with Proof of Stake, how can fork happen to make the double spending attack?
Thanks in advance :-)