What happens on the blockchain, stays on the blockchain.
Blockchain can also be called an immutable ledger. This is because it the very nature and purpose of the blockchain. Let's find out why?
The traditional ledger
Let's say that you want to buy a house. You go and pay the money and buy the home. Now, how will you prove to someone that you own the house? What is preventing you from going to any house and claiming it as your own? Well because you get a deed in exchange for the money. You need to go to the government and tell them that you have bought the house. To register it, they will store it in a ledger. Now, the ledger can be written or digital. And that is it.
Problems with traditional ledger
Now, there are a few problems with this system:
DeedYou are supposed to keep the deed with yourself. Now, the deed can be lost, burnt or pretty much anything. (Of course, there are provisions but we will conveniently ignore them.)
EntryThe record with the government is just an entry. It may be burnt or lost, assuming the ledger is physical. Or it may be deleted or erased by a malicious actor.
Note:- This is just an oversimplification for understanding, so don't draw any real-life conclusions. I know the system is very complicated.
Let's now suppose, the govt. adds this data on a blockchain. It is already a lot secure. Let's start with the benefits.
ImmutabilityAs the quote at the beginning said, anything that is on the blockchain is immutable. This means that the data cannot be edited or deleted once it has been put on the chain.
SharedIt means that the whole blockchain is shared across multiple nodes, so one bad actor can't change it all.
Cryptographic LinkWe also know that is the whole property of the chain that if you want to change one block it will make the whole chain invalid.
Let's say a few months pass and a lot of blocks were formed after yours. If someone decides to change one of the entries. Then, the hash of the block will change and cause the block's hash to change due to The Avalanche Effect. This will in turn cause the whole chain to be invalid. Also, we haven't discussed this yet but the system of peer-to-peer nodes will immediately correct the chain on the infected node. Therefore, we can say that it is nearly impossible to change one entry or one block.
That's it folks! This article is a part of the series and to be able to understand it better I recommend you to go through the series.