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Where better to start than to explain what a blockchain is. There are many articles that define and explain what blockchains are. I will attempt in the simplest way I know.

Let’s think about how we send money.

If John wants to give Mary $10, he can do it in a few ways:

John gives Mary $10 in cash.

When John gives Mary cash, there is no middle man and no record. Without a middle man, this transaction is quick. However, without a record, Mary could turn around tomorrow and say that John never gave her the $10.

John transfers $10 to Mary through Venmo, PayPal, PayNow, or a bank transfer.

When John transfers $10 to Mary through a bank or payments service, John gives instructions to the bank (sometimes through the payment service) to take money out of his account and put money into Mary’s account. The bank records this down and the record is called a ledger. A long time ago, banks may keep this record in a physical book. These days, banks keep these records on a server. John and Mary trust that the bank keeps these records safe and tables them accurately. Of course, banks can fail, records can be hacked, and they can also record these transactions inaccurately.

Now, there is a third way:

John sends Mary $10 on the blockchain.

A public blockchain (not all blockchains are public), like Bitcoin or Ethereum, is an open and transparent record of transactions — a ledger. Unlike bank records, copies of this ledger are distributed across many, many computers across the world and are not kept by one bank or company. They are decentralized.

When John transfers $10 to Mary on a blockchain, John flags to these computers on the blockchain that he is making this transaction. This network of computers then work to validate John’s transaction by solving complex mathematical problems. Then, the record of John’s transaction gets written on a ‘block' (think of this like a page of records). When this ‘block’ is filled, it gets added onto a chain (hence, blockchain). Once a block is added to the blockchain, to change it will affect all the subsequent blocks and require the agreement of a majority of computers on this network. This means that a hack or attempt to change transaction data on one or a few of these computers will not result in the blockchain records being altered. This is partly why we say that blockchain data is immutable.

On this very cute visualizer, you can watch in realtime transactions (little people) coming from different apps (buildings) being put on a block (bus) and the blocks being recorded on the blockchain (moving off).

Of course, this is a very simplified explanation of blockchain technology and there are many cool and nuanced intricacies to the tech. We also use the blockchain for more than just money transfers. This explanation covers some buzzwords you may have heard of before.

In healthcare, the most discussed potential application of blockchain technology is storing patient medical records on a blockchain. Using decentralized distributed ledger technology to store patient records means that we do not depend on health systems from keeping these records safe or to transfer patient records. This can improve data security and also help patients who cannot depend on a single health system (e.g. displaced refugees) to keep their medical data transferable and secure. There are also challenges in making this possible. We can talk more about this next time!

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