In 2008, Satoshi Nakamoto proposed an electronic cash system (bitcoin) that was completely implemented through peer-to-peer technology. The core value of the program is that it proposes a work-based proof-based solution that enables the cash system to operate in a peer-to-peer environment and prevents double-flower attacks. Bitcoin has been born for ten years, and countless digital currencies have been born, but the discussion of double-flower attacks seems to remain at 51% of Bitcoin attacks. In fact, our research has found that there are many other forms of practical digital currency double-flower attacks.

http://blogs.360.cn/post/double-spending-attack.html