This post introduces the concept of a majority (51%) attack and gives a short account of the role that Decred’s voters play in defending against these. I will briefly describe how majority attacks against Proof of Work (PoW) currencies work first, then explain how the additional Proof of Stake (PoS) component changes the dynamic in Decred’s case.
Performing a double spend attack means having the power to reorg (reorganize, or rewrite) the blockchain.