Weekly Bytes 1: What is a Blockchain?
Blockchain was invented in 1991 by Stuart Haber and W. Scott Stornetta to make a system to ensure documents were not tampered. It was not until 2009 when Bitcoin was released that the technology gained any attention.
block + chain = Blockchain :)
At a high level, a block is a bunch of information grouped together it’s usually made up of transactions, but it can be a whole host of different types of data. To chain these blocks together we use something called a hash.
A hash is an encrypted string of letters and numbers created from an input of, well, letters and numbers. Hashes are called “digital fingerprints” because they are completely unique. You can make the hash of anything, a tweet, a school essay, even this blog post! I could hash this blog, send the hash to a friend and if I ever went back and edited the blog, the friend could just hash the blog himself and see that the hash is different.
Here, I inputed the developer favorite “Hello World” and a hash was created. But if I change just one letter and make the input “Hello Worlds” you can see the hash is completely different.
So, if you have a block of transactions that you hash and change just one of those transactions then the entire block hash will change, letting someone know that the block was tampered with.
By now you understand that a block is just data grouped together. And you know that you can hash a block and will be able to tell if anything in the block changes based on the hash.
But how do you connect these blocks?
Well, this is where the chain comes in. Imagine three food items: tomatoes, marinara sauce, and a pizza.
To make marinara sauce you need tomatoes and to make a pizza you need tomatoes and marinara sauce. But if you change the tomatoes with apples, you also change the marinara sauce and the pizza, they become apple sauce and the worlds nastiest apple pie.
These foods represent blocks on the blockchain. To link these blocks, each block has the hash of the previous block inside itself. This is how you get the chain in blockchain. Just like changing the ingredients of the pizza, if you change a transaction in Block A then that changes the hash of Block B, and so on.
The tamper-proof nature of blockchain is how you can create a network of individuals all with the one copy of a blockchain that can’t be modified maliciously.
Each blockchain platform (Bitcoin, Ethereum, Ripple, etc.) has a different mechanism to come to an agreement about which transactions to add to the blockchain, this process is called consensus. We will cover this in a separate Weekly Bytes post, but for now just know that blockchains are append only. That means you can only add information not remove or edit.
Keep in mind, blockchains aren’t perfect. They’re still in a nascent stage, and there are some lingering problems with finality. One example is that on certain networks, such as Bitcoin and Ethereum, your transactions can take a while to be finalized. This is because you have to wait for a certain number of blocks to be added after yours (30 min — 2 hrs).
Read more about how blockchains can be manipulated from the recent Ethereum Classic 51% Attack.
There are a whole host of other challenges that blockchains still need to overcome. But overall, they provide a new framework to create some pretty awesome stuff!
I hope you enjoyed this quick overview of what a blockchain actually is. Of course this was a very high level overview but the purpose of Weekly Bytes is to bit by bit (pun intended!) build up your blockchain knowledge.
