Data on Bitcoin Can't be Changed & Why It Matters? | Let's Hack Bitcoin

Once an event is etched into Bitcoin blockchain records, it remains unchanged and unchangeable, forever cast in the digital stone of the blockchain. But why is this feature so important in the realm of Bitcoin?

A Quick Guide to Bitcoin
A Quick Guide to Bitcoin

I. Introduction

Picture an ancient monument, standing tall against the test of time, untouched and unchangeable. This monument is much like the Bitcoin blockchain, a powerful testament to the concept of immutability. Once an event is etched into its records, it remains unchanged and unchangeable, forever cast in the digital stone of the blockchain. But why is this feature so important in the realm of Bitcoin?

In this chapter, we'll explore the significance of immutability, dive into the mechanics of how the Bitcoin blockchain preserves this attribute, and discuss why it matters. Welcome to the journey through the unalterable paths of the Bitcoin blockchain.

II. Explanation of the Blockchain

Imagine a chain where each link is made not of steel, but of blocks of data. This is the essence of a blockchain. In the context of Bitcoin, each block contains a list of transactions that have taken place within a specific timeframe. But there's more to it than that.

These blocks are cryptographically linked to one another, forming a long, unbroken chain that goes all the way back to the very first block—known as the genesis block. Once a block is added to the chain, it becomes a permanent record of those transactions, viewable by anyone and alterable by no one.

But how does this chain maintain its integrity? How can it ensure that no one can change a block once it's been added? The answer lies in the powerful combination of cryptographic functions and network consensus mechanisms—a blend of technology and collective agreement that creates the backbone of the Bitcoin blockchain's unchangeable nature.

III. Immutability of the Blockchain

Immutability, a term borrowed from mathematics and computer science, means unchanging over time or unable to be changed. When applied to the blockchain, it signifies that once a block is added to the chain, it can't be altered or removed—just like you can't go back in time and change the past.

Every block on the Bitcoin blockchain contains a cryptographic hash of the previous block, a timestamp, and transaction data. This cryptographic hash is a unique digital fingerprint of the previous block's data. If someone tries to change the data in a block, this would change the block's hash, and since every subsequent block contains the hash of the previous block, changing one block would require changing every block that comes after it—a task that is computationally impractical given the power of the Bitcoin network.

This property of immutability has profound implications. It guarantees the integrity and permanence of transaction data, making the Bitcoin blockchain a trustworthy and tamper-proof ledger of Bitcoin transactions. No one can cheat the system by spending bitcoins they don't have or making a transaction disappear. This is a key aspect of Bitcoin's security and is crucial to its functioning as a decentralized digital currency.

IV. Cryptographic Hash Functions

The Bitcoin blockchain's immutability is largely thanks to cryptographic hash functions. But what exactly are these functions, and how do they work?

A hash function is a type of algorithm that takes an input, or 'message', and returns a fixed-size string of bytes. The output, or 'hash', typically looks random and changing even a tiny part of the input significantly alters the output.

In the context of Bitcoin, the hash function used is called SHA-256, which stands for 'Secure Hash Algorithm 256-bit'. It transforms any input into a long string of numbers and letters. Importantly, this transformation is a one-way street. While any input always produces the same hash, you can't figure out the original input based on the hash.

When a new block is added to the blockchain, it includes a hash of all the transaction data in the previous block. If someone tries to alter a transaction in a past block, it would change that block's hash, and thus the hash recorded in the next block, and the one after that, and so on.

Therefore, altering past transactions would require recomputing all those hashes, a task that would require an enormous amount of computational power. This is virtually impossible given the collective power of all the miners in the Bitcoin network who are constantly adding new blocks to the blockchain.

So, by using cryptographic hash functions, the Bitcoin blockchain ensures that its record of transactions is tamper-proof, providing security and trust in the network.

V. Proof of Work Consensus Mechanism

In Bitcoin's early days, anyone with a regular computer could mine new blocks. However, as the network grew, so did the need for a more robust system to keep the blockchain secure and maintain its immutability. Enter the Proof of Work (PoW) consensus mechanism.

Proof of Work is a system that requires miners to perform a certain amount of computational work to add a new block to the blockchain. This work involves solving a complex mathematical problem, which requires substantial computational power and energy resources. The first miner to solve the problem gets to add the new block and receive the block reward.

This mechanism is a critical part of maintaining the immutability of the blockchain. Changing any block's data would require redoing the work for that block and all subsequent blocks. Given the significant resources required, this would be virtually impossible.

Moreover, because many miners are competing to add new blocks, any malicious miner trying to alter past data would be outrun by the honest miners adding blocks with the correct blockchain history.

In this way, the Proof of Work consensus mechanism secures the Bitcoin blockchain and ensures that once a transaction has been recorded, it can't be changed. This maintains trust in the network and allows users to rely on the transaction history as an accurate record of all Bitcoin transactions.

VI. Chain of Blocks

The term "blockchain" is quite descriptive: it literally refers to a chain of blocks. But it's not a chain in the traditional sense of individual links connected end-to-end. Instead, each block in the Bitcoin blockchain is digitally connected to the one before it through a unique identifier called a hash.

Think of a hash as a digital fingerprint for a block of data. It's created using a cryptographic hash function, which takes the data in the block and converts it into a string of characters. Any change to the data, no matter how small, will dramatically alter the resulting hash.

This is where the genius of the blockchain comes in. Each block doesn't just contain its own hash; it also contains the hash of the previous block. This creates a direct link between each block and the one before it, forming the "chain".

If someone were to try and alter the data in a block, it would change that block's hash. But remember, that hash is also stored in the next block in the chain. This discrepancy would break the chain, immediately flagging the altered block. This makes any attempt to change data on the blockchain easily detectable, contributing to the immutability of the Bitcoin blockchain. This chain of blocks, securely linked through their hashes, acts as a public ledger of all Bitcoin transactions, one that cannot be tampered with without leaving obvious traces.

VII. Cost and Difficulty of Alterations

Now, you may wonder: what if someone had enough computational power to alter a block and then recalculate all the subsequent hashes, effectively covering their tracks? Technically, it's possible. But in reality, it's practically impossible.

Here's why: the Bitcoin network relies on a consensus mechanism known as Proof of Work. Miners compete to solve complex mathematical problems, and the first one to solve it gets to add the next block to the blockchain. This process is not only difficult, but it also requires a substantial amount of computational power and energy.

So, if someone wanted to alter a block, they wouldn't just have to solve the problem for that block. They'd also have to solve the problems for all the blocks that come after it, and they'd have to do it faster than the combined computational power of all the other miners on the network.

Moreover, the act of altering a block would alert the network to the discrepancy, as we mentioned before. Other miners, upon detecting the invalid block, would reject it and continue to build upon the original, unaltered blockchain.

As a result, the cost and difficulty of altering data on the blockchain are prohibitively high, making such alterations practically impossible. This is what makes the Bitcoin blockchain immutable and secure against fraud and tampering.

VIII. The 51% Attack

There's one scenario where the immutability of the blockchain could theoretically be threatened, and that's something called a 51% attack. This refers to a situation where a single entity or a group of colluding entities gain control of more than half of the network's mining power.

In this scenario, the controlling entity would have the ability to outcompete other miners and add new blocks to the blockchain at a faster rate. This would give them the power to manipulate the blockchain, including the ability to double-spend bitcoins, prevent transactions from being confirmed, or even alter past transactions.

Sounds scary, right? But before you panic, it's important to understand that pulling off a 51% attack is incredibly difficult. Not only would it require immense computational power, but it would also be extremely expensive. The cost of the necessary equipment and electricity would be astronomical.

More importantly, such an attack would likely destroy the value of Bitcoin. If people lost trust in Bitcoin's security, the price would plummet. So, the attackers, after spending a fortune to gain control of the network, would be left with a worthless currency.

While a 51% attack is theoretically possible, the economics of it make it highly unlikely. This is just another way that the design of the Bitcoin network protects the immutability of the blockchain.

IX. Trust and Transparency

If we think about traditional banking systems, they operate largely on trust. We trust the bank to keep track of our money, to accurately record our transactions, and to prevent unauthorized access to our accounts. But this trust-based model has its flaws. Banks can make mistakes, they can be hacked, or they could even engage in dishonest practices.

This is where Bitcoin and its immutable blockchain shine. The immutability of the blockchain is a fundamental part of why people trust Bitcoin. Once a transaction is confirmed and added to the blockchain, it can't be changed or erased. This means that every Bitcoin transaction is permanent and transparent.

In addition to this, the blockchain is open to everyone. Anybody can download a copy of the Bitcoin blockchain and see every transaction that has ever occurred. This level of transparency is unprecedented in the financial world and is another reason why people trust Bitcoin.

The immutability of the blockchain removes the need for trust in a central authority. Instead, trust is based on the unchangeable mathematics and code that underpin the Bitcoin network. This is a game-changer for the world of finance, and we'll continue to see the ripple effects of this innovation for years to come.

The immutability of the Bitcoin blockchain has implications that extend far beyond financial transactions. It's a feature that has the potential to revolutionize many different sectors, including the legal field.

Imagine a world where legal contracts are recorded on the blockchain. Once a contract is added to the blockchain, it becomes immutable. This means that the terms of the contract can't be altered without the agreement of all parties involved. This could significantly reduce disputes and increase the efficiency of legal proceedings.

Similarly, property rights could be recorded on the blockchain. This would provide a transparent and unchangeable record of ownership. This could be particularly valuable in countries where property records are poorly maintained.

However, the immutability of the blockchain also poses some potential challenges for the legal field. For example, what happens if an illegal contract is recorded on the blockchain? Or what if a mistake is made in the terms of a contract? These are questions that legal experts are currently grappling with.

It's clear that the immutability of the blockchain has far-reaching implications. As we continue to explore and understand this technology, it's likely that we'll see it being used in increasingly innovative ways. But as with any new technology, it's important to navigate these uncharted waters with caution.

XI. Future Implications of Immutability

Immutability, the defining feature of blockchain technology, has the potential to revolutionize many sectors beyond finance. This includes supply chain management, healthcare, and more. Let's take a quick look at some of these sectors:

  1. Supply Chain Management: The blockchain's immutable ledger can provide an accurate, tamper-proof record of a product's journey from manufacturer to consumer. This could help to prevent fraud, improve traceability, and provide consumers with more information about the products they buy.
  2. Healthcare: In the healthcare sector, the blockchain could be used to create immutable patient records, improving the accuracy of diagnoses and the effectiveness of treatments. Moreover, blockchain could enable secure sharing of patient data among authorized doctors or hospitals, enhancing patient care.
  3. Voting: Blockchain could also be used to conduct secure, tamper-proof voting, reducing the risk of fraud in elections and increasing public trust in the democratic process.
  4. Intellectual Property: Blockchain could provide a platform for the registration and protection of intellectual property rights, providing a clear record of ownership that could help to prevent infringement.
  5. Education: Educational institutions could issue degrees and certificates on the blockchain, providing an immutable record of a person's qualifications.

These are just a few examples of how the immutability of the blockchain could be leveraged in the future. As blockchain technology continues to evolve, it's likely that we'll see even more innovative uses emerge in the coming years. However, it's crucial to remember that the adoption of blockchain technology also brings challenges and risks, and these must be carefully managed to realize the technology's full potential.

XII. Summary and Preview

In this chapter, we delved deep into one of the most essential features of Bitcoin's blockchain: its immutability. We started with a broad understanding of the blockchain and then moved on to the concept of immutability. We learned how cryptographic hash functions and the Proof of Work consensus mechanism contribute to this immutability.

We also discovered that each block in the blockchain is connected to the previous one, a feature that makes any attempt to alter data easily detectable. We discussed the significant computational power and time required to change blockchain data, making such alterations practically impossible.

We further explored the concept of a 51% attack, explaining why such an attack is highly unlikely and not economically viable. The chapter highlighted how the immutability of the blockchain enhances trust and transparency, making Bitcoin a reliable financial system.

We also examined the potential legal implications of the blockchain's immutability, such as its use in recording legal contracts or property rights. Finally, we speculated on the future implications of the blockchain's immutability in various industries beyond finance, such as supply chain management, healthcare, voting, intellectual property, and education.

As we look ahead to the next chapter, we will continue our journey into the world of Bitcoin. We will delve into the intricacies of Bitcoin wallets: what they are, how they work, and why they are crucial for Bitcoin users. We will break down complex concepts into easy-to-understand segments, keeping our narrative engaging and straightforward. So, get ready to unlock the secrets of Bitcoin wallets in the next chapter!


  1. How are New bitcoins Minted?
  2. How Does Bitcoin Work? A High-Level Overview
  3. What is Uppercase Bitcoin vs. Lowercase bitcoin
  4. Why is the Supply of Bitcoins Limited to 21 Million?
  5. What's Bitcoin Halving & Why It Occurs Every 4 Years?
  6. What is a Bitcoin Transaction Exactly and How Does it Work?