Chapter 17: Introduction to Blockchain

This chapter provides an overview of the basic blockchain technology. In the next chapter we will see how a blockchain can be used to implement a cryptocurrency.

Simply put, a transaction is a record of some kind of exchange between two or more parties. For example, one party supplies a service, while a second party provides payment for the service. To make a payment, a party must possess some amount of funds and then must provide a signed statement transferring the funds to another party.

More generally, one can consider contracts between parties. A contract can be much more flexible than a transaction. It may include exit and penalty clauses and also may refer to unknown situations in the future. So, the language for writing a contract must be expressive enough to cover a whole multitude of tasks. We will come back to this issue when we discuss the interesting notion of smart contracts.