A blockchain is a decentralized digital ledger that secures data using cryptographic techniques. Transactions are validated by miners who use hashing algorithms to mine blocks that are added to the chain. The longest blockchain is considered the most trustworthy and secure. Blockchain technology has various use cases beyond cryptocurrency and is being explored in different industries.
Decentralized digital ledger technology called a blockchain is essentially a list of data records. Cryptography secures the data which is organized into blocks in chronological order.
Back in the early 1990s, Stuart Haber and W. Scott Stornetta created the earliest blockchain model to safeguard digital documents from data tampering using cryptographic techniques. This inspired other computer scientists and cryptography enthusiasts. Eventually, Bitcoin, the first cryptocurrency, was created.
Despite being older than cryptocurrencies, blockchain technology was only truly recognized after Bitcoin was introduced in 2008. Gradually, blockchain technology started gaining interest, and cryptocurrencies started receiving larger recognition.
While blockchain technology is typically used to document cryptocurrency transactions, it is suitable for other forms of digital data and has various use cases. The largest and most secure blockchain network is Bitcoin, which was designed with a balance of game theory and cryptography.
How Does Blockchain Work?
A blockchain is essentially a stable chain of blocks, with each block containing a list of confirmed transactions. The network of blockchain is maintained by multiple computers distributed globally, resulting in a decentralized database or ledger. Each node preserves a copy of the blockchain data and interacts with others to ensure consistency.
Blockchain Transactions and Mining
This global peer-to-peer network facilitates blockchain transactions and makes Bitcoin a decentralized digital currency that is immune to censorship and has no geographical limitations. Furthermore, blockchain systems are often considered trustless because they do not require any form of trust. Bitcoin is not controlled by a single authority.
Mining is a central aspect of Bitcoin and many other blockchains, but not all blockchains rely heavily on hashing algorithms for their mining process. Bitcoin specifically uses the SHA-256 algorithm (Secure hash algorithm 256 bits). This algorithm takes an input of any length and produces an output of a fixed length. The output is called a "hash" and consists of 64 characters (256 bits).
Executing a Blockchain Transaction
To better understand how a blockchain operates, let's consider a basic example of a transaction involving two people named Emily and Jack, and their cryptocurrency balance. Assume that Emily owes Jack 3 bitcoins.
To execute the transaction, Emily initiates a message that is broadcasted to all the miners in the network. The message contains Jack's address and the amount of bitcoin Emily intends to transfer. Additionally, Emily attaches a digital signature and her public key, which is validated by the miners to confirm her ownership of the tokens.
Mining the Block
The process of mining begins once the miners verify the validity of a transaction. When a transaction is confirmed, it is then added to a block with many other transactions. Miners then attempt to mine the block by running the SHA-256 algorithm on it. For the output to be considered valid, it must start with a certain number of 0s. The number of 0's required is determined by the "difficulty," which is adjusted based on the network's computing power.
Cryptocurrency miners strive to generate an output hash with a specific number of 0’s at the beginning during the mining process. To achieve this, they add what’s called a "nonce" to the block, which they modify randomly until a valid hash output is found. This is because even a small change in input will result in a completely different output.
Validating the Block
After successfully mining the block, the miner shares the newly mined block with other miners. The other miners then verify that the block is valid before adding it to their own copy of the blockchain, effectively completing the transaction. This step is crucial as the output hash from the previous block must also be included in the current block to link all blocks together, hence the term "blockchain."
Each miner maintains their own copy of the blockchain, and trust is established in the system based on the blockchain with the most computational work put into it, also known as the longest blockchain. If a miner tries to change a transaction in a previous block, the output hash for that block would change, leading to a domino effect of changes for all the subsequent hashes. To succeed in cheating the system, the miner would need more than 50% of the network's computing power, which is unlikely to happen. Such network attacks are referred to as 51% attacks.
Proof of Work and Proof of Stake
Proof of Work is the computer model utilized for producing blocks in cryptocurrency mining. Another model, Proof of Stake, is also available that requires less computing power and can handle more users while consuming less electricity.
Blockchain technology has revolutionized the way we think about digital data and transactions, providing a secure and decentralized network for storing and transferring information. Although the concept of blockchain was first introduced in the early 1990s, it was not until the creation of Bitcoin in 2008 that blockchain technology began to gain mainstream recognition. Today, blockchain technology is being used in various industries beyond cryptocurrency, and its potential applications are just beginning to be explored.