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What Makes a Blockchain Network Immutable? Immutability Explained

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22nd Nov, 2022
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What Makes a Blockchain Network Immutable? Immutability Explained

One of the attributes that the blockchain is often associated with is its immutability. In its technical nature, Blockchain is an immutable database, and you cannot manipulate data that’s already in the blockchain. Hash value is a unique value, identifying one block. It depends on the block’s content, so each block has its unique hash value, and it’s identifying this block only. Therefore each block can reference or point to the block before, which means the four-block is taking a reference to the third one is taking a reference to the second, and so on. So that reference is made by the hash value.

The simplest way to explain the blockchain process can be: Let’s, for example, implement the blockchain in a simple yet flawed bank transaction. Suppose, A wants to send money to B. The transaction is represented as a “block.” This block is broadcast to every party in the network. Those in the network approve whether the transaction taking place is valid. As iterations go on, a chain is formed, showing transparency in transactions. Lastly, the cash flows from A to B, and the transaction is complete.

Here, in the above example, blockchain’s immutable nature is visible, making it flawless. The combination of validations done with the blockchain hashing process and cryptography makes it immutable.

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How is Immutability Achieved?

One of the key elements that make blockchain immutable is cryptographic hashes, which is why blockchain is immutable. The main advantage of hash is that it cannot be reverse-engineered. That’s the reason why it is so popular. The most popular hash function is SHA-256, i.e., Secure Hash Algorithm 256.

The block header’s content is identical to strings of random letters and numbers. For example, the previous hash’s length is typically 32 bytes, and it represents four sets of 8 bits characters in each set. It provides you with the original 256 bits when you divide 256 by 32.

The Merkle root is the basic portion of the data structure. It depicts that transactions are not changed over the network. It denotes a summary of each transaction. Moreover, the timestamp shows the time when the transaction was done and orders transactions sequentially. The nonce is the number incremented when performing hashing to solve a particular block. It contains a set of decimal numbers in polygon networks.

Hashing involves feeding input via a cryptographic algorithm to obtain an output. Every block in the blockchain is connected via the bound cryptographically and hashing process. The rule on a standard public blockchain can only be broken via a hard fork that creates a new chain that is incompatible with the older one. Remember that hashing can’t be reverse-engineered.

The immutability is achieved because the algorithm is a subset of the parameters that connect all network blocks. These blocks are sequentially secured, and no modification is allowed. If somebody attempts to change the data or input on the block, the existing block will disconnect from all the earlier blocks. Thus, a malicious attacker or user who intends to change blockchain data should modify all the blocks before the existing block, but this task is difficult.

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There’s an input that goes into the hash function with a checksum as the end-product. In the below image, we can see how ‘Blockchain is Disruptive’ goes as an input, after which hashing occurs, resulting in an encrypted output as a checksum.


Here in the below image, after hashing of a block, the checksum of it is an input to another block, which will generate a checksum as an output. Each iteration here will result in a different checksum every time. In a block, the transactional data is processed with the previous hash along with the Meta-Data and TX Data Hash, which altogether is hashed. That’s why the checksum generated at every block is always unique. This certainly explains why blockchain is immutable to some extent.

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In this framework, exchanges confirmed by a blockchain network incorporate squares of data implanted with timestamps, which is made sure about by a hashing cycle. It interfaces together and consolidates the hash of the past square. This instrument builds up the ordered chain that joins each square.

The hashing consistently incorporates the meta-information of the past square while producing another hash for it, which sets up a connection between the square and the chain at that point gets “rugged.” The facts confirm this is a strong system. In any case, there are a few difficulties that this component needs to survive.

Immutable Blockchain: Tamper Evident vs. Tamper Proof

Usually, blockchain immutability is misunderstood even by industry enthusiasts. To understand blockchain immutability, you must know the difference between Tamper Proof and Tamper Evident.

Tamper Evident means an object can’t be tampered with without noticing it.

Tamper Proof means that an object can’t be tampered with.

Tamper proof is essential to achieve immutability; just Tamper Evident is inadequate. Various blockchains in polygon networks falsely claim immutability, but they are simply Tamper Evident


Note that blockchain immutability is relative. We can go through a few real-life examples to understand this.

Example-1: Suppose you try removing the toothpaste from a tube. But putting it back inside is difficult. This shows that it has been tampered with, so it is an example of a Tamper Evident.


Example-2: Emails that are sent can’t be unsent. The emails can be very immutable. But you can always convince the email’s recipient or the individual operating the mail server to delete it. It may be challenging and involve the risk of detection in crypto networks. This is an example of Tamper Evident.


Threats to Blockchain’s Immutability

Consider blockchain networks that support transactions like the Bitcoin blockchain or a blockchain underlying a cryptocurrency. These networks can translate to being a double spending attack.

This decentralized technology is devoid of a single entity accessing a particular network’s strings. But, if data miners work in a group and gather most of the hashing power, blockchain immutability can pose a risk. Presently, it is easy to deal with such an attack in polygon networks owing to the ability to rent out mining capacity and growth in the mining marketplaces.

The same may be challenging and expensive to perform in large blockchain networks, specifically those running via the proof-of-work consensus protocol. The reason is it needs huge hashing power in crypto networks. Blockchain startups and smaller coins are at risk, as demonstrated by the double spending attacks conducted on Litecoin Cash, Bitcoin Gold, Monacoin, etc.

The attackers could reverse high-value transactions and spend the corresponding amounts for a second-time usage. This was possible by adapting the transaction data that was expected to be immutable in a permissioned blockchain.


Benefits of Blockchain Network Immutability

  1. High Security:

Immutability guarantees blockchain transactions’ security and makes sure the data is less susceptible to hacking. Hacking is common in cryptocurrency, but the target has been primarily smart contracts developed on top of blockchains. Certain blockchains, for example, Cardano, are unaffected by hacking.

2. Integrity:

Blockchains don’t require trust. If someone tries to change the data, the block breaks and can’t become part of the chain. Therefore, the stored data’s integrity is maintained.  Validation is a constant process. The invalid blocks can’t be a part of the chain.

3 . Easy reconciliation:

The blockchain transactions’ immutable characteristic removes the dependency on extra auditing. It provides proof to participants who transact on a tamper-proof network.

4. Time-saving:

Transaction time is 10 minutes on blockchains like Bitcoin. Some latest blockchains like Solana have a block time of less than a second. Generally, settlement systems and traditional ledgers are slow. The identical transactions can take several days to be updated in a permissioned blockchain network.

5. Source of Truth:

Certain industries like agriculture, pharmaceutical, and food industries are investing in immutable ledgers. The corresponding immutable ledger is implemented with blockchain to avoid adulteration. It also ascertains the source’s legitimacy and makes sure the process of sourcing raw materials is less abusive.

The potential to generate a transactional ledger’s comprehensive and undeniable history facilitates easy and efficient auditing. Those companies that can prove that their data is not tampered with will attain a noteworthy competitive advantage in the context of permissioned blockchain.

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Read: How to Make a Successful Career in Blockchain? Everything You Need to Know


The biggest advantage of blockchain is that the data cannot be altered, whereas, as seen in the traditional databases, the data can be modified and deleted easily. And if any instance occurs where the data is tampered with, the blockchain breaks. Making changes in both disconnected and live blockchain advancements is very troublesome.

When individuals allude to the blockchain as permanent, it implies that it is hard to make changes without conspiracy, not that the information can’t be changed. Hence, it answers the question of why blockchain is immutable. Furthermore, this innovation has both positive and negative ramifications for information security.

Ledgers that send blockchain innovation can ensure the full history and information trail of an application. When an exchange joins the blockchain, it remains there to portray the record up to that point in time. The respectability of the chain can be approved whenever by basically re-ascertaining the square hashes — if an inconsistency exists between block information and its comparing hash, that implies the exchanges are not legitimate. This permits associations and its industry controllers to identify information dabbling rapidly. This ensures complete data integrity.

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Future Aspects

upGrad has got blockchain courses available, and that too designed by the most prestigious IIIT-B. Pioneering such a domain can result in great value addition to your technology stack. And having such a skill in your portfolio always weighs more. Along with developing your skill, some additional elements that are provided by upGrad are commendable. It allows you to be part of the network, which consists of industry experts. This will enable you to know their thought process and mentality.

No doubt, there will be a wide range of applications of blockchain implemented soon, but you need to be updated with the daily advancements done in this technology. At upGrad, you learn as well as implement your skills in projects that allow you to enhance your knowledge. And one of the unique things you get at upGrad is that you can opt for a No Cost EMI option and go easy on your pockets. Hence, opting for such courses is always encouraged.

There are plenty of business solutions that can be provided with the help of blockchains. Right from easy integrations to better transparency, great efficiency and improved security make its kind. Then again, for endeavors and different foundations that need to share an information base across hierarchical limits securely, verification of-work permanence has neither rhyme nor reason. Not exclusively is it astoundingly costly. However, it permits any adequately propelled member to namelessly hold onto control of the chain and blue pencil or opposite exchanges.

For digital currency adherents who need to stay away from officially sanctioned cash and the conventional financial framework, it unveils ideal sense to have confidence in a proof-of-work blockchain whose permanence lies on financial matters instead of confided in parties. Furthermore, most likely, they trust that digital currencies will just get safer, as their worth and mining limit keep developing.

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This word ‘immutable’ is utilized to indicate something which can never be adjusted or changed. When a blockchain exchange has gotten an adequate degree of approval, some cryptography guarantees that it can never be supplanted or turned around. This imprints blockchains as unique in relation to standard records or data sets, in which data can be altered and erased freely.

If you’re interested to become a blockchain developer and build smart contracts and chain codes, checkout IIIT-B & upGrad’s Advanced certificate program in blockchain technology.

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Mayank Sahu

Blog Author
Mayank Sahu is the Program Marketing Manager with upGrad for all emerging technology vertical. His past experience is in analytics industry extensively in healthcare Domain. Mayank has completed his Graduation from IIT Delhi.
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Frequently Asked Questions (FAQs)

1What is Proof-of-Work?

Proof-of-Work is a blockchain algorithm that deals with the creation of a new block that can be added to the blockchain. This algorithm helps validate the transaction or a block that is added to the chain. This process involves miners who compete together to solve a complex mathematical puzzle. Miners are those people who are responsible for authenticating transactions. The miner who solves it first gains the privilege of adding the block to the chain and a monetary reward. Bitcoin, which is one of the most famous cryptocurrency works on this algorithm.

2How does blockchain ensure security?

Blockchain is secure because it works on the principle of hashing and cryptography. It is secure because it works on a distributed ledger system. Generally, a single ledger becomes a single point of failure, and any disruption might compromise the entire data. However, blockchain stores the same data at multiple nodes distributed around the world, and the data cannot be modified. Even if the data in one node is modified, it can be easily detected with the help of the hash values of other blocks in the chain. The data in the block is stored by using encryption techniques and is safe. Hence, blockchain ensures security.

3Can blockchain networks be created based on the level of privacy one needs, or is it always public?

Yes, there are different types of blockchain networks one can use based on their privacy requirements. Public blockchain networks are accessible for everyone to read and verify data. Once data enters into a block, it's permanent. Apart from this, individuals can have private and hybrid networks as well. In a private blockchain network, one must have permission to read and verify data, which is given only to authorized people to ensure privacy. Hybrid model deals with keeping some data private and some public. Hence, blockchain is adaptable to the needs of privacy.

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