Deep Dive into
Blockchain

A blockchain is a decentralized digital ledger — a record book that is shared across thousands of computers around the world simultaneously.

Instead of one bank or company keeping the official record, everyone on the network holds an identical copy. New entries are bundled into "blocks" and added to a growing "chain" — and once written, they cannot be altered.

This creates a record that is transparent (anyone can read it), secure (changing it requires overwhelming computing power), and decentralized (no single authority controls it). [6]

Imagine a small town where every property sale is recorded in a public ledger kept at the town hall. One official controls that ledger. If the official makes a mistake — or is corrupt — the record changes and no one can prove otherwise.

Now imagine instead that every single resident keeps an identical copy of that ledger at home. When a new sale happens, everyone updates their copy at the same time. If one person tries to change their copy to say they own a property they don't, the other thousands of copies all disagree — and the cheat is instantly exposed.

That is what a blockchain does — except instead of property records, it records financial transactions, and instead of a town, it spans the entire globe.

Every block in the Bitcoin blockchain contains three key pieces of information, bundled together like an envelope:

• The Header — metadata about the block: when it was created, a reference to the previous block, and the solution to the mathematical puzzle (the "nonce").
• The Transactions — a list of every Bitcoin payment confirmed in that block (Bitcoin currently holds around 2,000–3,000 transactions per block).
• The Hash — a unique digital fingerprint of this block's entire contents. Change even one character inside, and the fingerprint changes completely.

The word "chain" in blockchain refers to how every new block contains the hash (fingerprint) of the previous block inside its header. This creates an unbreakable chain stretching back to the very first block ever created — called the Genesis Block, mined by Satoshi Nakamoto on January 3, 2009.

If anyone tried to alter an old block — say, to change a transaction — that block's hash would change. That would break the link to the next block. And the block after that. And so on, all the way forward through the entire chain. You would need to redo all of that mathematical work faster than the entire rest of the network — a practical impossibility.

Three properties combine to make blockchain extraordinarily difficult to tamper with:

• Cryptographic hashing — Any change to a block's data produces a completely different hash, instantly exposing the tampering.
• Chained links — Because every block references the previous block's hash, changing one block breaks every block that follows it.
• Decentralization — Tens of thousands of independent computers all hold an identical copy. A cheat would have to overpower more than half of all that computing power simultaneously — a near-impossibility called the "51% attack problem."

The idea of a blockchain did not spring fully-formed from Satoshi Nakamoto's mind. It built on decades of cryptographic research. Here is the key history: [6][7][8]

Bitcoin was the first practical application of blockchain technology. Its blockchain has several distinctive features:

• One new block every ~10 minutes — The difficulty of the mathematical puzzle adjusts automatically every two weeks to maintain this pace, regardless of how much computing power is on the network.
• The Halving — Every 210,000 blocks (roughly every 4 years), the reward miners receive for creating a new block is cut in half. This is how Bitcoin's supply is kept scarce and predictable. The most recent halving occurred in April 2024.
• Immutability — Not a single confirmed Bitcoin transaction has ever been reversed. The record is permanent.
• Transparency — Every transaction ever made on Bitcoin's blockchain is publicly visible. You can view them at mempool.space.

Maple Bitcoin School

To learn more about Bitcoin and build wealth, join Maple Bitcoin School — a Canadian Bitcoin education community. Designed for learning, not for buying Bitcoin.

Referral link — Ted Lee may receive a small reward if you sign up. This does not affect your cost.

More on BTC.TedLee.ca