Interesting side fact. Proof of work was used before in 2004 to prevent spam but it failed. Nakamoto put that concept in a merkle tree. https://m-cacm.acm.org/

Interesting side fact. Proof of work was used before in 2004 to prevent spam but it failed. Nakamoto put that concept in a merkle tree. https://m-cacm.acm.org/magazines/2019/8/238347-the-history-of-digital-spam/fulltext#R26 https://m-cacm.acm.org/magazines/2019/8/238347-the-history-o...