The blockchain is a distributed database of records of all transactions or digital event that have been executed and shared among participating parties. Each transaction verified by the majority of participants of the system. It contains every single record of each transaction. BitCoin is the most popular cryptocurrency an example of the blockchain. Blockchain hereby provides a universal state layer, a universal data set that every actor can trust, even though they might not know or trust each other. This new form of distributed data storage and management also avoids the double-spending problem of existing value transfer over the Internet. Ideas around cryptographically secured P2P networks have been discussed in the academic environment in different evolutionary stages, mostly in theoretical papers, since the 1980s. However, before the emergence of Bitcoin, there has never been a practical implementation of a P2P network that managed to avoid the double-spending problem, without the need for trusted intermediaries guaranteeing value exchange.