Peercoin, also known as PPCoin, is a peer-to-peer cryptocurrency utilizing proof-of-stake and proof-of-work systems. Peercoin is based on an August 2012 paper which listed the authors as Scott Nadal and Sunny King. Sunny King, who also created Primecoin, is a pseudonym. Nadal’s involvement had diminished by November 2013, leaving King as Peercoin’s sole core developer. Peercoin was inspired by Bitcoin, and it shares much of the source code and technical implementation of Bitcoin. The Peercoin source code is distributed under the MIT/X11 software license.