Immutability…. We use this word in daily routine to signify a thing, which can never change. Whereas, in the blockchain, this word is referring to the worldwide transactions. Which is adjust by the participants. Here, the basic approach is, once the block blockchain transactions are complete, it cannot replace or reverse by other transactions.
So, the theory goes. Because
Saint Augustine states, “The highest good, than which there is no higher, is the blockchain. And consequently it is immutably good, hence truly eternal and truly immortal.”
Two prominent examples are,
- Under certain conditions, through some necessary adjustment transactions, history can change itself. Here, the question is arises, it easy to bring new changes in the content of the blockchain? Is it really easy?
- According to cryptocurrency advocates, immutability achieves only in case of decentralization of economic mechanism. Which is not proper fall at the private sector of the blockchain. Because, they totally depend on the collective behavior of a known group of validators, who are not trustworthy.
Above two circumstances are totally wrong. Because in blockchain there is no immutability thing exist. The proper question is,
Under which circumstance the blockchain will or will not change? And,
Do those conditions match with the problem, we are trying to solve?
Instead, the chain’s behavior depends on the network of a computer system. Before we get into the detail of how we ‘ll summarize the basics of blockchain first.
Brief discussion on Blockchain
A blockchain system is running onto the different set of nodes. Which may be in control of different companies. There is no individual node who control the others. While nodes are connecting with each other through a proper network. These nodes generate and propagate transactions and rapidly spread to other nodes via digital operations in some kind of database.
Every new upcoming transaction is verified by an independent node. Following are some terms of verification;
1.it is totally in obedience of blockchain rule and regulations.
2. it is completely a digital structure
3. If any transaction passes the test of nodes. It will enter to the local list of not confirm transactions means directly in the memory pool. While others will enter in the orphan pool. In addition, pass transactions will be forward to its peers.
With some intervals, a node which contains the set of as-yet unconfirmed transactions on the network generates a new block. Each block contains the hash (32-byt). Therefore, by creating a little block chain, each block includes the timestamp. Accordingly, link to the previous block via its hash.
Blocks move and verified by nodes across the network like transactions. For the acceptance by the nodes, a block must contain proper transactions including no conflict with other ones. Whereas, with the confirmation of the test, it is entering into the local blockchain and transactions are confirm. Any transaction which conflict with others will discard immediately. Whether they are in memory pool or orphan pool.
Participation of the chain, make the strategy to ensure the generation of blocks. This ensures indicates that any kind of node. whether it is an individual or a group has no ability to take hold of the blockchain’s content.
Authentication and testing
Proof-of-work a public blockchain allow its users to generate block who has the ability to solve the tricky and fiendishly mathematical puzzle. Whereas, to prevent minority control in private blockchains, blocks are signed by authorized members. In order to create a lawful chain, a product needs to legalize validator by using mining diversity.
Two different validator nodes can generate conflicting blocks when both have the same previous points. However, fork happens. While different blocks are seen by nodes and leading them to have the different opinion about the chain’s history. These forks are resolved on the arrival of new blocks on branches by a blockchain software.
Shorter branch’s node spool back its last block and replay these two blocks on the longer one. Unfortunately, if you are unlucky and both branches will extend. Then the conflict will be resolved by the third and so on. In addition, with the increase in fork’s length, the probability of a fork persisting drops increases. After a small number of the blocks, it can be reduced to zero in private blockchain.
Here, the most important thing to remember is, each node is controlled by a particular person. Where blockchain has not authority to ask some changes in transactions. The main purpose of the chain is to help in sync. But, if participants want to change the rule, no one has authority to stop them.
That is why we need to stop asking about the immutability of blockchain. Because the answer is “no”. Arguably, we consider the conditions under which it needs changes.
Public chain’s mutability
Let’s start with the above mention two examples. We will take the start with the claim that authorization process. Which used in blockchain cannot bring true immutability by public chains. e.g.
Ethereum blockchain faces a devastating situation in June 2016. “the DAO”, loophole found by someone. In which, $250 million were invested and start draining its speed. Which distract the both investor and creator’s intentions. After few days, the ethereum software updated to prevent from hackers. It was publicly supported by Vitalik Buterin that ethereum users will control their own computer system. As a result, a large number of users, blockchain comes with the new name and rules is ethereum. Whereas, minority reject this idea and keep going with ethereum classic. There were more choices for names like ethereum compromise or ethereum pure. Whatever, democracy is the democracy, and everyone has their own rights voice. In addition, ethereum is ten times more than ethereum classic.
Now, we will take a common way, in which blockchain’s immutability will be dilute. Recall that mining of bitcoin and ethereum uses proof of work scheme. Where you get a reward for solving a tricky puzzle. In addition, this reward increases the potential of the users and they solve the relating issues more efficiently. Network continually adjust the rate of block creation. In addition, 10 minutes in bitcoin or 15 seconds in
Immutability of blockchain
Bitcoin has faced the factor difficulty of 350,000x from last 5 years. Today, bitcoin mining is on hardware devices with cheap electricity and in cold weather. Antminer S9 mines the block 10,000 faster than a desktop system. Which burns 10 times more electricity than a system with cost $1089.
To undermine the immutability of bitcoin blockchain, you need to install more mining capacity, then the other network creating 51% attack first. Secondly, through proper testing and approval, mine your own secret branches. Finally, at desired time, release your secret branch to the network anonymously. Then, the whole process of a transaction will be without any scams or hacking issue. It is not easy to install a huge program. It needs a lot of money and electricity as well. And a common man or country who has the shortage of both. Unfortunately, are not able to adopt this way for immutability of bitcoin blockchain.
Let’s estimate the cost of a 51% attack which reverses a year of bitcoin transactions. At the current bitcoin price of $1500 and reward of 15 bitcoins (including transaction fees) per 10-minute block. Miners earn around $1.2 billion per year ($1500 × 15 × 6 × 24 × 365). Reasonably, they are not losing money. So, the total expense should be in the same range.
Rewriteable private chains
Now, let’s have a ride to private blockchains. Which was established for the needs of government and well-reputed organizations. According to the organization’s perspective, immutability is the commercial, legal and regulatory non-starter. Because it allows attacking the network anonymously. whereas, immutability can also be ashore in good behavior of other institutions. With whom, they have authority to sue or sign a contract. It is a bonus because private blockchains are less costly to run. Since blocks need just a node’s approval and digital signature. When a number of validators follow the rules. As a result, you get cheaper and stronger immutability than other digital currencies offer. Furthermore, the percentage of immutability may decrease when participants in chain decide to do so together.
Immutability is nuanced
People who don’t like the traditional banking system and government’s currency are perfect to use proof of work blockchain. Whose immutability rely on economic terms instead of participants. It may be an expensive operation. when parties agree to live with government or wealthy actors and bringing down the network. Accordingly, they believe that cryptocurrency technology and its value continue to grow and it will get more secure.
Finally, for most permission blockchain use cases. We probably don’t want validator nodes to be able to easily and cheaply substitute old blocks in the chain. As Dave Birch says “the way to correct a wrong debit is with a correct credit”. Rather than pretending that the debit never took place. Nonetheless, for those cases where we do need the extra flexibility, chameleon hashes help make blockchains a practical choice.