Blockchain Facts

What Is a Blockchain?

A blockchain is a distributed database or ledger shared among a computer network's nodes. They are best known for their crucial role in cryptocurrency systems for maintaining a secure and decentralized record of transactions, but they are not limited to cryptocurrency uses. Blockchains can be used to make data in any industry immutable—the term used to describe the inability to be altered.
Because there is no way to change a block, the only trust needed is at the point where a user or program enters data. This aspect reduces the need for trusted third parties, which are usually auditors or other humans that add costs and make mistakes.
Since Bitcoin's introduction in 2009, blockchain uses have exploded via the creation of various cryptocurrencies, decentralized finance (DeFi) applications, non-fungible tokens (NFTs), and smart contracts.

KEY TAKEAWAYS

• Blockchain is a type of shared database that differs from a typical database in the way it stores information; blockchains store data in blocks linked together via cryptography.
• Different types of information can be stored on a blockchain, but the most common use for transactions has been as a ledger. 
• In Bitcoin’s case, blockchain is decentralized so that no single person or group has control—instead, all users collectively retain control.
• Decentralized blockchains are immutable, which means that the data entered is irreversible. For Bitcoin, transactions are permanently recorded and viewable to anyone.

How Does a Blockchain Work?

You might be familiar with spreadsheets or databases. A blockchain is somewhat similar because it is a database where information is entered and stored. But the key difference between a traditional database or spreadsheet and a blockchain is how the data is structured and accessed.

A blockchain consists of programs called scripts that conduct the tasks you usually would in a database: Entering and accessing information and saving and storing it somewhere. A blockchain is distributed, which means multiple copies are saved on many machines, and they must all match for it to be valid.
The blockchain collects transaction information and enters it into a block, like a cell in a spreadsheet containing information. Once it is full, the information is run through an encryption algorithm, which creates a hexadecimal number called the hash.
The hash is then entered into the following block header and encrypted with the other information in the block. This creates a series of blocks that are chained together.

Transaction Process

Transactions follow a specific process, depending on the blockchain they are taking place on. For example, on Bitcoin's blockchain, if you initiate a transaction using your cryptocurrency wallet—the application that provides an interface for the blockchain—it starts a sequence of events.
In Bitcoin, your transaction is sent to a memory pool, where it is stored and queued until a miner or validator picks it up. Once it is entered into a block and the block fills up with transactions, it is closed and encrypted using an encryption algorithm. Then, the mining begins.
The entire network works simultaneously, trying to "solve" the hash. Each one generates a random hash except for the "nonce," short for number used once.
Every miner starts with a nonce of zero, which is appended to their randomly-generated hash. If that number isn't equal to or less than the target hash, a value of one is added to the nonce, and a new block hash is generated. This continues until a miner generates a valid hash, winning the race and receiving the reward.
Generating random hashes until a specific value is found is the "proof-of-work" you hear so much about—it "proves" the miner did the work. The amount of work it takes to validate the hash is why the Bitcoin network consumes so much computational power and energy.
Once a block is closed, a transaction is complete. However, the block is not considered to be confirmed until five other blocks have been validated. Confirmation takes the network about one hour to complete because it averages just under 10 minutes per block (the first block with your transaction and five following blocks multiplied by 10 equals about 60 minutes).
Not all blockchains follow this process. For instance, the Ethereum network randomly chooses one validator from all users with ether staked to validate blocks, which are then confirmed by the network. This is much faster and less energy intensive than Bitcoin's process.

Blockchain Decentralization

A blockchain allows the data in a database to be spread out among several network nodes—computers or devices running software for the blockchain—at various locations. This not only creates redundancy but maintains the fidelity of the data. For example, if someone tries to alter a record at one instance of the database, the other nodes would prevent it from happening. This way, no single node within the network can alter information held within it.
Because of this distribution—and the encrypted proof that work was done—the information and history (like the transactions in cryptocurrency) are irreversible. Such a record could be a list of transactions (such as with a cryptocurrency), but it also is possible for a blockchain to hold a variety of other information like legal contracts, state identifications, or a company’s inventory.

Blockchain Transparency

Because of the decentralized nature of the Bitcoin blockchain, all transactions can be transparently viewed by either having a personal node or using blockchain explorers that allow anyone to see transactions occurring live. Each node has its own copy of the chain that gets updated as fresh blocks are confirmed and added. This means that if you wanted to, you could track a bitcoin wherever it goes. 
For example, exchanges have been hacked in the past, resulting in the loss of large amounts of cryptocurrency. While the hackers may have been anonymous—except for their wallet address—the crypto they extracted are easily traceable because the wallet addresses are published on the blockchain.
Of course, the records stored in the Bitcoin blockchain (as well as most others) are encrypted. This means that only the person assigned an address can reveal their identity. As a result, blockchain users can remain anonymous while preserving transparency.

Is Blockchain Secure?

Blockchain technology achieves decentralized security and trust in several ways. To begin with, new blocks are always stored linearly and chronologically. That is, they are always added to the “end” of the blockchain. After a block has been added to the end of the blockchain, previous blocks cannot be changed.
A change in any data changes the hash of the block it was in. Because each block contains the previous block's hash, a change in one would change the following blocks. The network would reject an altered block because the hashes would not match.
Not all blockchains are 100% impenetrable. They are distributed ledgers that use code to create the security level they have become known for. If there are vulnerabilities in the coding, they can be exploited.
For instance, imagine that a hacker runs a node on a blockchain network and wants to alter a blockchain and steal cryptocurrency from everyone else. If they were to change their copy, they would have to convince the other nodes that their copy was the valid one.
They would need to control a majority of the network to do this and insert it at just the right moment. This is known as a 51% attack because you need to control more than 50% of the network to attempt it.
Timing would be everything in this type of attack—by the time the hacker takes any action, the network is likely to have moved past the blocks they were trying to alter. This is because the rate at which these networks hash is exceptionally fast—the Bitcoin network hashed at 348.1 exahashes per second (18 zeros) on April 21, 2023.1

Bitcoin vs. Blockchain

Blockchain technology was first outlined in 1991 by Stuart Haber and W. Scott Stornetta, two researchers who wanted to implement a system where document timestamps could not be tampered with. But it wasn’t until almost two decades later, with the launch of Bitcoin in January 2009, that blockchain had its first real-world application.2
The Bitcoin protocol is built on a blockchain. In a research paper introducing the digital currency, Bitcoin’s pseudonymous creator, Satoshi Nakamoto, referred to it as “a new electronic cash system that’s fully peer-to-peer, with no trusted third party.”3
The key thing to understand is that Bitcoin uses blockchain as a means to transparently record a ledger of payments or other transactions between parties.

Blockchain

Blockchain can be used to immutably record any number of data points. This could be in the form of transactions, votes in an election, product inventories, state identifications, deeds to homes, and much more. 
Currently, tens of thousands of projects are looking to implement blockchains in various ways to help society other than just recording transactions—for example, as a way to vote securely in democratic elections.
The nature of blockchain’s immutability means that fraudulent voting would become far more difficult. For example, a voting system could work such that each country's citizens would be issued a single cryptocurrency or token.
Each candidate would then be given a specific wallet address, and the voters would send their token or crypto to the address of whichever candidate for whom they wish to vote. The transparent and traceable nature of blockchain would eliminate the need for human vote counting and the ability of bad actors to tamper with physical ballots.

Blockchain vs. Banks

Blockchains have been heralded as a disruptive force in the finance sector, especially with the functions of payments and banking. However, banks and decentralized blockchains are vastly different.
To see how a bank differs from blockchain, let’s compare the banking system to Bitcoin’s blockchain implementation.