Far from being an unprecedented breakthrough, with unintended consequences, the blockchain technology stack is a culmination of decades of cryptography and security research.

The 1970s cryptography breakthrough of the Merkle tree and the distributed hash tables of the 1990s combine to create autonomy, fault tolerance and scalability for distributed systems. They're the tools that built famous decentralised applications like BitTorrent, Napster and Freenet.Bitcoin's most impressive contribution is recognising the synergies between this field of distributed communications and file sharing systems, and digital currencies, which had seen many false starts prior to Bitcoin's success since 2009.

The key was Hashcash, a system proposed in 1997 to limit and suppress email spam and denial-of-service attacks. Hashcash is an algorithm that requires the sacrifice of processing power as a security mechanism. This proof-of-work creates the incentive structure and network verification that now powers cryptocurrencies.

The final step is the addition of smart contracts to the blockchain stack, a name coined by Nick Szabo as early as 1993. Smart contracts are algorithmic; a type of self-executing code which enables more complex asset transfer and the automated exchange of rights. These are the building blocks of a complete programming language, and the more advanced blockchain applications such as those envisioned by Ethereum.

What we get is a set of security tools that are very good at coordination between mutually unknown actors and secure data or value transfer. We think of blockchains as having four key characteristics to this end: they're cryptography-based, distributed, peer to peer, and, in many cases, open source.