HOW DOES BITCOIN WORK?

FROM THE BLOCKCHAIN TO THE NETWORK NODES

INTRODUCTION

Since its creation in 2009 by the enigmatic Satoshi Nakamoto, Bitcoin has intrigued and fascinated in equal measure. For some, it's simply a digital currency. For others, it's a technological revolution capable of profoundly transforming our financial system. Understanding how Bitcoin works, however, doesn't require being a computer scientist or mathematician. Behind this innovation lies a set of relatively simple mechanisms that allow a global network of computers to verify, record, and secure transactions without relying on a central authority. To grasp this unique architecture, one must understand four fundamental elements: the decentralized network, nodes, transactions, and blocks.

THE DECENTRALIZED NETWORK

Unlike traditional banking systems, Bitcoin does not rely on any central institution. There is no central bank, nor is there a single server controlling the system. Instead, the Bitcoin network consists of thousands of computers distributed around the world, all interconnected and running the same software. This architecture is called a decentralized network. Any participant can join the network, download the Bitcoin software, and contribute to its operation. The absence of a central authority means that no single entity can change the system's rules, censor transactions, or control the currency. The protocol operates according to public and transparent rules that all participants abide by. This decentralization is one of the pillars of Bitcoin's security and resilience. Even if part of the network were to disappear or be attacked, the remaining machines would continue to operate the system. It is this distributed structure that allows Bitcoin to exist as an independent, global monetary infrastructure.

THE KNOTS

The computers that participate in the Bitcoin network are called nodes. Their role is essential: they verify transactions, enforce the protocol rules, and maintain a complete copy of the transaction history. Each node thus possesses a copy of the blockchain, the public ledger where all transactions performed since the network's creation are recorded. When a new transaction appears, the nodes verify it to ensure it complies with the system's rules. For example, they check that the sender actually owns the bitcoins they are trying to transfer and that the transaction is not a double-spending attempt. This collective verification guarantees that no one can cheat. Even if a malicious actor tries to introduce a fraudulent transaction, the other nodes in the network will immediately reject it. Thus, trust is not based on a central institution but on a verification system distributed among thousands of independent computers.

TRANSACTIONS

A Bitcoin transaction is simply a transfer of value between two addresses on the network. When someone sends bitcoins to another person, they digitally sign the transaction using their private key. This cryptographic signature proves that they are indeed the owner of the funds they wish to transfer. Once created, the transaction is broadcast across the network. Nodes receive it, verify it, and then propagate it to other participants. The transaction then enters a queue called a mempool, where it waits to be confirmed by miners. This system allows anyone in the world to send value directly to another person, without a banking intermediary. A Bitcoin transaction can cross the globe in seconds and be confirmed by the network in minutes.

THE BLOCKS

Transactions are not recorded individually on the blockchain. They are grouped into sets called blocks. Each block contains a number of transactions along with a cryptographic reference to the previous block. This mechanism creates a chain of chronologically linked blocks: the blockchain. Each new block is added to the chain, forming a public and immutable ledger of all transactions. Once a block is added to the blockchain, the information it contains becomes extremely difficult to alter. To change a single past transaction would require recalculating all subsequent blocks and exceeding the computing power of the rest of the network. In practice, this makes the Bitcoin blockchain virtually impossible to falsify. It is this combination of a decentralized network, node verification, cryptography, and recording in successive blocks that allows Bitcoin to function as an open, secure, and independent monetary system.

PROOF OF WORK

At the heart of Bitcoin's operation lies a mechanism called proof of work. This system, conceived long before Bitcoin's creation by cryptographer Adam Back, secures the network while preventing fraud and transaction manipulation. Proof of work is based on a simple idea: to add a new block to the blockchain, the network's computers must solve an extremely complex cryptographic problem. This process requires significant computing power and consumes energy. The machines that participate in this competition are called miners. Miners gather pending transactions into a block and then attempt to solve a specific mathematical equation. The first machine to find a valid solution can submit its block to the rest of the network. The other nodes then verify the result. If everything conforms to the protocol's rules, the block is added to the blockchain and becomes a new page in the global ledger of Bitcoin transactions. This mechanism plays a crucial role in the system's security. To alter the transaction history, an attacker would need to control computing power greater than that of the entire network combined. However, the computing power that secures Bitcoin is now enormous and distributed worldwide. Attacking the network would require colossal financial and energy resources, making such an attack extremely unlikely. Proof-of-work thus transforms energy and computing power into digital security. This system allows Bitcoin to operate without a central authority while guaranteeing the integrity of its public ledger.

MINERS AND THE CREATION OF BITCOIN

The machines that participate in the proof-of-work process are called miners. Their role is to secure the network while validating transactions. In exchange for this work, they receive a reward in the form of new bitcoins. When a miner successfully solves the cryptographic problem that adds a new block to the blockchain, they receive what is called a block reward. This reward consists of two elements: the transaction fees included in the block and a new coin creation programmed by the Bitcoin protocol itself. This mechanism is how new bitcoins enter circulation. Unlike traditional currencies, whose creation depends on central bank decisions, the issuance of bitcoins is entirely determined by the protocol's code. The rate of creation is predictable and transparent to all network participants. The competition between miners is global. Thousands of specialized machines operate continuously, attempting to find the next block. These machines perform billions of calculations per second, forming a gigantic computing power distributed across the globe. This collective power, called the hashrate, represents the security strength of the Bitcoin network. But this money creation isn't constant. Approximately every four years, an event called a halving reduces the reward given to miners by half. This mechanism gradually slows the issuance of new bitcoins and increases the asset's scarcity. In the long run, it helps make Bitcoin a predictable monetary system, whose monetary policy is embedded in the protocol itself.

THE 21 MILLION LIMIT

One of Bitcoin's most fundamental aspects is its maximum supply of 21 million units. This rule has been part of the protocol since its inception and constitutes one of the system's most radical characteristics. Unlike traditional currencies, which can be created in unlimited quantities by central banks, Bitcoin has a strictly limited supply. The total number of bitcoins that will ever exist is encoded in the network's code and can only be changed with the unanimous agreement of all participants. In practice, such a change is extremely unlikely because it would undermine the very principle of scarcity that underpins the system's value. The gradual reduction of the block reward through halvings is progressively driving the network towards this limit. As the years go by, fewer and fewer new bitcoins are created. By around the year 2140, all 21 million bitcoins will have been issued. This characteristic profoundly distinguishes Bitcoin from fiat currencies. In traditional monetary systems, money creation can be used as a tool of economic policy, often leading to a continuous increase in the money supply. This expansion can result in a loss of purchasing power in the long term, a phenomenon known as inflation. Bitcoin offers the opposite approach. Its monetary policy is predictable, transparent, and independent of political decisions. This programmed scarcity brings Bitcoin closer to certain natural resources like gold, whose quantity is limited and difficult to increase. For many observers, this property transforms Bitcoin into a form of scarce digital asset, sometimes described as digital gold. In a world where currencies can be created almost without limit, the promise of a currency with a strictly defined supply represents a profound break with modern monetary history.

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