Immutability

While sounding complex, immutability is a fancy word that describes something that cannot be changed. The “state” or “being” of an object or of data in question, say like a public blockchain’s record of transaction data, stays the same and can’t be altered after creation.

The opposite of immutable is changeable, alterable, or variable.

When talking about blockchains, and Bitcoin specifically, immutability is a core and critical feature, and it’s talked about primarily in two ways.

In the first way, immutability refers to the ability of a blockchain to maintain its transaction history in a way that it can’t be altered, replaced or manipulated by some entity, like a government or another business or even miners working to validate transactions for the network.

Bitcoin’s hash function enforces the network’s append-only block creation characteristic.

When a block is added to the chain, the hash of the previous block is embedded in the newly created block.

If the previous block’s hash were changed in any way, the current block’s hash would also change, invalidating the entire block.

This makes the transaction data on the Bitcoin network immutable or unalterable. Any changes to one block would affect the next block, and a change to that block would alter a 3^rd block. And so on. Altering one block means all subsequent blocks would also need altering.

In the second way, and again referencing the Bitcoin network, Bitcoin’s proof-of-work (PoW) consensus protocol makes it so that the network’s monetary ruleset can never be changed.

Thousands of Bitcoin nodes run independently, some operated by large businesses or miner pools, and others run by individuals, in a peer-to-peer network.

All nodes have a common voice, but no single node will act as the master or as a single point of failure.

All the nodes run the same code and they all agree on the same rules governing the network.

They all also must vote and agree to any changes proposed to the network. Blockchain-based voting systems, then by extension, can’t be altered or votes removed.

This aspect of shared responsibility and validation of transactions, block creation, and agreement on rules changes provides trust to network participants that Bitcoin’s monetary policy can’t be changed by just one node but will require thousands of nodes to all agree.

Related Terms

Full Node

A type of node that participates in a blockchain network, performing some function for the network, like securing the network or validating transaction data. A full node stores a complete copy of the blockchain data. Information about every block and the recorded transactions within each block is available in the full copy of the blockchain.

Bitcoin (BTC)

Bitcoin (BTC) is most well known as a digital decentralized cryptocurrency, without a central bank or single administrator, that can be sent from user to user on the peer-to-peer Bitcoin network without the need for intermediaries, such as payment gateways or banks or routing services. Think of bitcoin as Internet money, that you can send and receive directly, to and from anyone, and you can use it to pay for stuff.

Genesis Block

The very first block or first few blocks recorded on a blockchain or blockchain-based protocol. The genesis block is often called Block 0 or Block 1. The genesis block sets the foundation for the rest of the blocks that are added to form a chain of blocks. That’s where we get the word “blockchain”. The most famous genesis block, and the very first Bitcoin block, called the Genesis Block, was created on January 3rd, 2009, by Bitcoin’s infamous and mysterious creator, Satoshi Nakamoto. Some consider this date to be the start of the cryptocurrency revolution – the start of it all!

Blockchain

Blockchain networks are at the heart of cryptocurrencies. A blockchain is a database, or digital ledger, made up of a series of interconnected blocks containing transaction data created on the network over some period of time. Each block in a blockchain also contains a unique identifier unlike any other block in the chain called a hash. Think of the hash as a fingerprint identifying that block for all other blocks. Distributed ledger technology (DLT) is another name frequently used in relation to blockchains.

Soft Fork

In relation to blockchain technology, a soft fork involves introducing changes to a blockchain’s underlining protocol or software that are minor in nature. These software updates can take the form of new blockchain functionality, upgrades to network performance, enhancements that correct security issues, or even changes to the consensus rules that govern how blocks are created and validated on a blockchain. Forks are necessary for providing decentralized blockchains a way to make changes to the blockchain since there isn’t a central authority governing all aspects of blockchain development and evolution.