What Is a Blockchain?
A blockchain is a distributed database or ledger shared across a computer network's nodes. They are best known for their crucial role in cryptocurrency systems, 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—meaning it cannot be altered.
Since a block can’t be changed, the only trust needed is at the point where a user or program enters data. This reduces the need for trusted third parties, such as auditors or other humans, who add costs and can make mistakes.
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. 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 Bitcoin blockchain collects transaction information and enters it into a 4MB file called a block (different blockchains have different size blocks). Once the block is full, the block data is run through a cryptographic hash function, which creates a hexadecimal number called the block header hash.
The hash is then entered into the following block header and encrypted with the other information in that block's header, creating a chain of blocks, hence the name “blockchain.”
Transaction Process
Transactions follow a specific process, depending on the blockchain. 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 picks it up. Once it is entered into a block and the block fills up with transactions, it is closed, and the mining begins.
Every node in the network proposes its own blocks in this way because they all choose different transactions. Each works on their own blocks, trying to find a solution to the difficulty target, using the "nonce," short for number used once.
The nonce value is a field in the block header that is changeable, and its value incrementally increases with every mining attempt. If the resulting hash isn't equal to or less than the target hash, a value of one is added to the nonce, a new hash is generated, and so on. The nonce rolls over about every 4.5 billion attempts (which takes less than one second) and uses another value called the extra nonce as an additional counter. This continues until a miner generates a valid hash, winning the race and receiving the reward.
Once a block is closed, a transaction is complete. However, the block is not considered 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 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 creates redundancy and maintains the fidelity of the data. For example, if someone tries to alter a record on one node, the other nodes would prevent it from happening by comparing block hashes. This way, no single node can alter information within the chain.
Because of this distribution—and the encrypted proof that work was done—the blockchain data, such as transaction history, becomes irreversible. Such a record could be a list of transactions, but private blockchains can also hold a variety of other information like legal contracts, state identifications, or a company's inventory. Most blockchains wouldn't "store" these items directly; they would likely be sent through a hashing algorithm and represented on the blockchain by a token.
Blockchain Transparency
Because of the decentralized nature of the Bitcoin blockchain, all transactions can be transparently viewed by downloading and inspecting them or by 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 is easily traceable because the wallet addresses are stored 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, 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 altered.
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 generally reject an altered block because the hashes would not match. However, a change can be accomplished on smaller blockchain networks.
A new and smaller chain might be susceptible to this kind of attack, but the attacker would need at least half of the computational power of the network (a 51% attack). On the Bitcoin and other larger blockchains, this is nearly impossible. 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 rapid—the Bitcoin network hashed at a rate of around 640 exahashes per second (18 zeros) as of September 2024.
The Ethereum blockchain is not likely to be hacked either—again, the attackers would need to control more than half of the blockchain's staked ether. As of September 2024, over 33.8 million ETH has been staked by more than one million validators. An attacker or a group would need to own over 17 million ETH, and be randomly selected to validate blocks enough times to get their blocks implemented.
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.
Bitcoin
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.”
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. The data can be 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 could then be given a specific wallet address, and the voters would send their token or crypto to the address of whichever candidate they wish to vote for. 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.
How Are Blockchains Used?
As we now know, blocks on Bitcoin’s blockchain store transactional data. Today, tens of thousands of other cryptocurrencies run on a blockchain. But it turns out that blockchain can be a reliable way to store other types of data as well.
Some companies experimenting with blockchain include Walmart, Pfizer, AIG, Siemens, and Unilever, among others. For example, IBM has created its Food Trust blockchain to trace the journey that food products take to get to their locations.
Why do this? The food industry has seen countless outbreaks of E. coli, salmonella, and listeria; in some cases, hazardous materials were accidentally introduced to foods. In the past, it has taken weeks to find the source of these outbreaks or the cause of sickness from what people are eating.
Read Also: How to Create an NFT
Benefits of Blockchains
Accuracy of the Chain
Transactions on the blockchain network are approved by thousands of computers and devices. This removes almost all people from the verification process, resulting in less human error and an accurate record of information. Even if a computer on the network were to make a computational mistake, the error would only be made to one copy of the blockchain and not be accepted by the rest of the network.
Cost Reductions
Typically, consumers pay a bank to verify a transaction or a notary to sign a document. Blockchain eliminates the need for third-party verification—and, with it, their associated costs. For example, business owners incur a small fee when they accept credit card payments because banks and payment-processing companies have to process those transactions. Bitcoin, on the other hand, does not have a central authority and has limited transaction fees.
Decentralization
Blockchain does not store any of its information in a central location. Instead, the blockchain is copied and spread across a network of computers. Whenever a new block is added to the blockchain, every computer on the network updates its blockchain to reflect the change.
By spreading that information across a network, rather than storing it in one central database, blockchain becomes significantly more difficult to tamper with.
Efficient Transactions
Transactions placed through a central authority can take up to a few days to settle. If you attempt to deposit a check on Friday evening, for example, you may not actually see funds in your account until Monday morning. Financial institutions operate during business hours, usually five days a week—but a blockchain runs 24 hours a day, seven days a week, and 365 days a year.
On some blockchains, transactions can be completed and considered secure in minutes. This is particularly useful for cross-border trades, which usually take much longer because of time zone issues and the fact that all parties must confirm payment processing.
Private Transactions
Many blockchain networks operate as public databases, meaning anyone with an internet connection can view a list of the network’s transaction history. Although users can access transaction details, they cannot access identifying information about the users making those transactions. It is a common misperception that blockchain networks like Bitcoin are fully anonymous; they are actually pseudonymous because there is a viewable address that can be associated with a user if the information gets out.
Secure Transactions
Once a transaction is recorded, its authenticity must be verified by the blockchain network. After the transaction is validated, it is added to the blockchain block. Each block on the blockchain contains its unique hash and the unique hash of the block before it. Therefore, the blocks cannot be altered once the network confirms them.
Transparency
Many blockchains are entirely open source. This means that everyone can view its code. This gives auditors the ability to review cryptocurrencies like Bitcoin for security. However, it also means there is no real authority on who controls Bitcoin’s code or how it is edited. Because of this, anyone can suggest changes or upgrades to the system. If a majority of the network users agree that the new version of the code with the upgrade is sound and worthwhile, then Bitcoin can be updated.
The Bottom Line
With many practical applications for the technology already being implemented and explored, blockchain is finally making a name for itself in no small part because of Bitcoin and cryptocurrency. As a buzzword on the tongue of every investor across the globe, blockchain stands to make business and government operations more accurate, efficient, secure, and cheap, with fewer intermediaries.