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ETC Proof of Work Course: 9. The Meaning of Immutability in POW

Donald McIntyre
Education, Series

You can listen to or watch this video here:

In the previous class, 8, we talked about how proof of work (POW) promotes basic rights on a global scale.

One of the most important features of POW that guarantees these basic rights is the immutability of the ledger with accounts, balances, and smart contracts.

In this class, 9, we will explain the concept of immutability in the blockchain industry and why it is important.

The topics that we will touch will be:

  • What is immutability
  • Why immutability must be a core value
  • Immutability of past history
  • Immutability of future history
  • How POW guarantees immutability
  • Only users control their money, dapps, and assets

What Is Immutability in POW Blockchains?


Immutability means that things don’t change overtime, or that they are unable to be changed.

In the blockchain industry, we could say that accounts, balances, and dapps are unable to be changed by third parties who usually don’t have the best interests of users in mind.

These “third parties” may be just thieves who want to steal wealth, corporations or special interests who want to extract value from this wealth, or governments who want to control and direct people’s lives and money.

On POW blockchains, the principle of immutability guarantees that addresses, cryptocurrency balances, and dapps will not be changed by third parties.

Why Immutability Must Be A Core Value

Truly decentralized public blockchains, as systems exposed to the environment with no protection other than their internal security, need to have especially strong immutability at the protocol layer.

Immutability is not only about directly securing the integrity and continuity of distributed basic rights, as we explained in our previous class, but also includes all the parts and parameters of those blockchains that assure those rights.

Immutability is achieved with decentralization, and decentralization is only achieved with the proof of work consensus mechanism.

Immutability must be a core value in blockchain design so that the risk of damaging the integrity of the database, that contains the accounts, balances, and dapps people use, is minimized.

Immutability of Past History

Immutability in a public POW blockchain may be divided in immutability of the past history or of the future history.

Both must be guaranteed.

The immutability of past history is enforced by cryptography and blockchain design.

If a blockchain uses public key cryptography for users to own and control their accounts and balances, and uses proof of work to build blocks, then the immutability of past history is guaranteed by the protocol itself and its internal design.

This objective form of guaranteeing immutability and thus security may be called “physical layer security”.

Immutability of Future History

When The DAO hard fork that violated immutability in Ethereum happened in 2016, thus making it split from the original chain, ETC, one of the false arguments developers used was that the immutability of the chain had not been violated because the change was done looking forward, not backward in time.

What they did was that the hacker’s account had $50 million dollars one moment and then zero the next, but the past history was not touched. They called this a “state change” and claimed it did not violate immutability because the history of the hacker’s account was not touched!

This is why immutability must be a core value in blockchain ecosystems, to prevent this kind of trickery.

However, POW systems such as Bitcoin and ETC are so widespread, global, and decentralized that to coordinate a state change that violates future immutability would be practically impossible. This is what is called “social layer security”.

How POW Guarantees Immutability

POW guarantees immutability of both past and future history in two ways:

Past history: As each block in POW blockchains is built using a lot of electricity, computing power, and capital, then to change past history would be enormously onerous to anyone who would want to attack the chain. As time passes by, accounts and balances become even more immutable because to change the history would require all the work to be done again, not only for the block in question but for all subsequent blocks as well.

Future history: Because POW guarantees true decentralization on a worldwide basis, then miners and node operators are distributed across many nations, regions, cultures, religions, languages, and jurisdictions, making it extremely difficult to coordinate changes that would violate immutability.

Only Users Control Their Money, Dapps, and Assets

When we talk about immutability, we talk about accounts, balances, and decentralized applications being practically impossible to change by third parties.

This does not mean that users who are owners of their assets on Bitcoin or ETC will not be able to change their property, move balances, or pay for things!

In fact, the only way to change the state of accounts and balances in POW blockchains is by their owners using their private keys to sign transactions. With their private keys, users can fully control their addresses, cryptocurrencies, other assets, or applications.

This is why private key management is so important and such a paradigm change in the financial industry.

Thank you for reading this article!

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