Since AI is popping up everywhere, you undoubtedly hear the term “blockchain” far less often.
Let’s bring it back for a moment, purely out of nostalgia, and uncover what it actually is. Technology explained in a nutshell.
What does it stand for?
Block. And chain. A chain of blocks. Yes, really. This is another one of those terms coined by speakers at networking events. Just like the “cloud” is essentially just a data center, a blockchain at its core is simply a clever way to link a list of hashes together.
What does it do?
Okay, I hear you thinking—how does a simple list of hashes become a chain of blocks? Let me explain.
You can see the blocks as pieces of information. For example, a message you send to a friend: “hello, how are you?”. Your friend replies: “hi, I’m doing well, and you?”. That creates a sequence. A chain.
The idea of blockchain is that you can authenticate that chain: you can prove that each message is exactly as you claim it is.
How does it work?
A blockchain is a list of hashes. A hash is the result of a mathematical function. The special thing about a hash is that you can create one extremely quickly, but it is practically impossible to reverse it to reveal the original content.
For example: suppose the word “hello” would result in a hash value of 10. In reality, a hash is a long string of characters, but the idea is the same.
If all you see is the number 10, you have no way of knowing that the original message was “hello”. But if you hash “hello” again in the same way and you get 10 again, you know the content matches. The hash confirms the message without revealing its content.
What’s the point?
Sometimes you need to prove that information has not been altered. With a digital agreement, for example, you could store a hash of the document. Later you can prove it hasn’t been modified, because the same content will always produce the same hash.
With a sequence of information—also known as a blockchain—you take it a step further. You can verify not just a single document, but an entire series.
A concrete example
- Message: “hello”, timestamp: Feb 25, 2020, previous hash: none, hash: abcd1234
- Message: “hi”, timestamp: Feb 26, 2020, previous hash: abcd1234, hash: efgh5678
Each next message uses the hash of the previous message as part of the new calculation. This means the second message can only be correct if the first one is correct too, and so on. Later you can verify that the entire conversation is authentic, letter by letter.
Combine this with an external party where you publish the hashes—outside your own control—and you have solid evidence. Both parties have the same hashes and an external reference. The hashes contain no content themselves and can be safely shared. It’s a chain of control values that lets you prove that data is authentic, unchanged, and in the correct order.
Finally
Why isn’t it called a “hash trail” in English? No idea. “Blockchain” probably just sounds better from a marketing perspective. But the power of blockchain lies entirely in hashing—a mathematical marvel that has been the foundation of digital security and authenticity for many years.