The simplest way to describe a blockchain is that it is a list of transactions or a ledger.
When talking about a Bitcoin blockchain (there are different types of blockchains) it is in terms of a transaction. [I, Sovereign, am trading “X” for .5 bitcoin.] When the transaction is complete I leave my fingerprint on it as well as a unique identifier number (called a hash) so it cant be replicated.
Now, lets say I want to buy something with bitcoin. You, the reader, charge me .5 bitcoin for “X” and now another entry in the ledger has been generated containing your fingerprint with unique transaction ID number as well as my old transaction ID from the previous transaction. That new transaction is called a “block.”
When boiled down, within a block there are three parts:
- Contents (ledger of bitcoin being traded from X to Y)
- Your finger print (w/unique ID number)
- My finger print (w/unique ID number)
As transactions are being entered into the ledger, what was once considered the “New fingerprint” would be considered the “Old fingerprint” of each subsequent block. This functions as the chain that links all blocks together. If you follow the links, eventually you will find what is called the “genesis block.” The first block in the chain marking the first transaction.
THESE CHAINS CANNOT BE BROKEN!
So, what happens if someone tampers with the ledger? Lets say a hacker changes one of the hash in a block which is actually very easy to do. Essentially, every block after the tampered one would be nulled out and the chain would be broken. The tampered block and every subsequent block are now worthless.
That is the blockchain SUPER SIMPLIFIED.
Another way of thinking about the blockchain is this:
Contents + Old Fingerprint = New Fingerprint
New Fingerprint grows up, meets Contents and they make their own New Fingerprint and so on and so forth…
When talking about bitcoin specifically, there are some other security measures put in place to further deter one from breaking the link for ANY reason.
I am talking about Peer-to-Peer verification.
On top of the built-in verification system, there are other participants in the transaction. Their purpose is to witness the transaction. They take note of all the details within the block, and then when needed, provide that info to re-link the broken chain.
So, if a chain is broken, it wont stay broken for long. If there is a bad link, it will be replaced with the proper one according to all the witnesses. By the way, there could potentially be thousands of witnesses. Any bitcoin miner can join.
Here is how the Peer-to-peer works.
You agree to allow some of your computers processing power in exchange for the chance to receive some bitcoin. That processing power you are lending is actually algorithm processing. You are now a witness. Your personal record of that blockchain you witnessed will be used to verify the validity of the links in that chain over and over and over. There must be consensus between all the witnesses, by at least 50%.
Another security measure for bitcoin specifically is called proof of work. Basically, it means out of all the algorithms presented when mining bitcoin, most of them will be decoys. Worthless wastes of time. This extends the time and increases the difficulty of processing blocks. Thus decreasing the chance of tampering.
There you have it…
the most basic breakdown of the blockchain ever, with some additional info related to bitcoin.
Don’t think of blockchain as synonymous with bitcoin. The blockchain could be used for anything! I know that hospitals are using blockchain to verify records of patients. And banks are using it to allow the IRS to track money leaving the country.
A decent (but dry) book about blockchain is “The Internet of Money” by Andreas Antonopoulos. He talks about bitcoin but almost half of the book is dedicated to blockchain.
And Now that you know some of the terminology, this video will be much more digestible..even though its probably the most simplified explanation of bitcoin and on the internet.