Blockchain is used in different contexts, and their use is predicted to grow more common and extend to new application areas. The most well-known use case is Bitcoin, which uses the blockchain in its fundamental form. Other application areas, to name a few, are governance, tourism, industry, financial sector as a whole and different research and development endeavors.

This introductory course to blockchain, First Notes on Blockchain, withholds the general definition of blockchain, basic vocabulary and structures associated with blockchain, a non-technical introduction to application areas, and gentle basics of mathematics and coding of blockchains. As an introductory course, the contents are by no means complete and fast R&D work related to blockchain makes attaining such a complete content impossible. Basics of implementing real-world blockchain is discussed, but the main focus is on understanding of blockchain. The ideal result of taking the course would be that the student could apply their attained principled knowledge to find a new application area for the blockchain.

Course includes theory, which are built paying attention to clarity and approachability. Figures and videos are included to further clarify the most demanding parts. The course is divided into three independent wholes, enumerated with the roman numerals I, II and III. After each whole, a video submission is required to continue to the next part. The first part I deals with most prominent application areas, as well as mathematics of blockchain. The second part II is about smart contracts, legislation and business models. The last part III engage in coding, future and societal effects of blockchains.

We discuss mathematics quite early on because it is the basis of any blockchain’s ability to keep the system intact. Otherwise, we discuss things in rising order of complexity. This method gives students from different backgrounds a possibility to get an understanding of the topic while making it possible for ambitious reader to find all he or she or they need to continue their studies. For these reasons, every Chapter finishes with a Section giving further reading. These sources are not included into the course and are not part of the evaluation. They are only there to give more information of the Chapter’s topic.

What is a blockchain? An educational quote from a 2018 article in the New Yorker (for the quotes used here, see also Tochen 2019) provides the reader a starting point:

“Broadly speaking, a blockchain is an evolving record of all transactions that is maintained, simultaneously and in common, by every computer in the network of that blockchain, be it Ethereum, Bitcoin, or Monero. Think, as some have suggested, of a dusty leather-bound ledger in a Dickensian counting house, a record of every transaction relevant to that practice. Except that every accountant in London, and in Calcutta, has the same ledger, and when one adds a line to his own the addition appears in all of them. Once a transaction is affirmed, it will--theoretically, anyway--be in the ledger forever, unalterable and unerasable. With blockchains, the records, under a kind of cryptographic seal, are distributed to all and belong to no one. You can't revise them, because everyone is watching, and because the software will reject it if you try. There is no Undo button. Each block is essentially a bundle of transactions, with a tracking notation, represented in a bit of cryptographic code known as a "hash," of all the transactions in the past. Each new block in the chain contains all the information (or, really, via the hash, a secure reference to all the information) contained in the previous one, all the way back to the first one, the so-called genesis block.” (Paumgarten 2018)

Iansiti and Lakhani (2017) give a more detailed description of blockchain, stating five traits of blockchain technology:

1 Distributed database: Each participant in the blockchain has access to the entire database. No single party controls the data in the blockchain, and every party can directly verily the data transactions of every other party.

2 Peer-to-peer transmission: Communication occurs directly between peers rather than through a central depository.

3 Transparency with pseudonymity: Each blockchain user (also known as a "node") has a unique 30-plus-character alphanumeric address that identifies the user.

4 Irreversibility of records: Once a transaction is entered in the database and the accounts are updated, the records cannot be altered because they are linked to every prior recorded transaction. Computational algorithms ensure that each blockchain transaction is permanent, in chronological order, and available to all other users. (This feature is often described as "immutability," which, at least in theory, prevents hacking into a blockchain.) (Orcutt 2019)

5 Computational logic: Blockchain transactions can be programmed and thus enable users to set up algorithms and rules and automatically trigger transactions between nodes.

The question of what is a blockchain can be answered in many ways and has multiple answers, depending on from which viewpoint the question is dealt with. Mathematically blockchains are cryptography (hereby the name of cryptocurrencies, discussed in Chapter 2).

Mathematics of blockchain can also be about elliptic curve digital signature algorithm (ECDSA), which is shortly discussed in Chapter 3. In addition, governance can according to some be developed through blockchain technologies with diminished need for human safeguarding, which in turn cuts costs (Chapter 4). On the other hand, finance sector discusses blockchains in accordance with personalised investment, which comes with its pros and cons, discussed in part II, Chapter 5. In IT, blockchains are called distributed systems. Currently, the reader can view blockchain primarily as a tool with multiple uses, some which are only being discovered.

After completing this course, students should have the basic knowledge of blockchains, considering different fields of study, including but not limited to law, finance, logistics, governance, mathematics and IT. The differences between these fields are many but learning the basics of blockchain demands knowledge on all of them. Students should also be able to see the connections between these fields in the context of blockchains. If learning on blockchains is continued in a more specialised courses, having the general knowledge of different areas could ease learning in later studies.