Among many other things first introduced with Peercoin, such as destroying the transaction fee, a coherent inflation rate, or minimum dust limit, the original authors of Peercoin were also the first to implement Proof-Of-Stake consensus. Peercoin minting requires a full node and complete blockchain history. To participate in proof-of-stake consensus

Open letter from the Peercoin Project Leader and Foundation Board Member, Peerchemist, to the community, supporters, and sympathizers of the project. You will often see me argue that Peercoin is the only true Proof-of-Stake chain because it allows everyone to be a "validator" or simply a "block