Three rules about time-traveling and blockchain
- If something happened, it happened.
- Traveling into the past is hard – but maybe not impossible. Changing a single detail can create Time Paradox, so watch – don’t touch.
- We travel into the future all the time. Second by second. While you were reading it, you have already moved ahead in 10 seconds to the future.
Now let’s imply these rules to our topic:
- If the block is created, it’s created.
- Changing the existing block is hard – but maybe not impossible. By altering a single piece of information, you can create Chain Paradox and it will not work.
- We create new blocks all the time. 5 seconds for one. While you were reading it, there are already 2 blocks built.
So what is this Blockchain?
Blockchain is a system of computers that we use to share, store, and secure data. This can be anything: a well-known bitcoin, personal documents, photos of your cats, or any other piece of information people decide to share. Every transaction and information sharing creates a new block. It is connected to the previous ones, building up a chain. This chain of blocks is a blockchain. Yeah, the name of the technology is very straightforward. So, how does it work?
Jack wants to send me 45 bitcoins. If he sets a small commission fee, I will get it in a day, or half a day, or several hours. Miners do not like to be underpaid so they put a priority on the orders with higher commission. If he pays more I get my money faster. As soon as the transaction finishes successfully a new block is added to the system of chains and it contains the information about the sender (John), receiver (me), and amount of bitcoins (45). The blocks are being built in chronological order. However, it’s not the only connection they have. What makes them truly united and secure is a hash. Just as your fingerprint, voice, and face are unique to you, the hash is unique to each block and its information. It consists of 32 digits. Anytime the miners create a block – the hash is generated. Any time you alter the information in the existing block, the hash changes as well.
Let’s say I want to rob Jack and alter the information about the transaction. I come up with a plan. First, I change the number of bitcoins I obtained to 20 instead of 45. Then I call John and tell him that he cheated and underpaid. If John doesn’t believe, I show him the info about the transaction and get my additional 25 bitcoins. Sounds pretty easy, if there wasn’t for the fact that each block contains not only its own hash but also the hash of the previous block. To deceive Jack, I will have to change the hashes in all subsequent blocks that were built after mine so that they would match. In theory, it is achievable. However, there are thousands and millions of them.