When that new block is added to the blockchain, it works and becomes publicly available for anyone to view.

What is distributed ledger?

Each computer in the blockchain network has its own copy of the blockchain, which means that there are thousands or millions of copies of the same blockchain. Although each copy of the blockchain is identical, spreading that information across a network of computers makes the information more difficult to manipulate. With blockchain, there isn’t a single, definitive account of events that can be manipulated. Instead, a hacker would need to manipulate every copy of the blockchain on the network. This is what is meant by blockchain being a “distributed” ledger.

What is security of blockchain?

Blockchain technology accounts for the issues of security and trust in several ways. First, 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, it is very difficult to go back and alter the contents of the block. That’s because each block contains its own hash, along with the hash of the block before it. Hash codes are created by a math function that turns digital information into a string of numbers and letters. If that information is edited in any way, the hash code changes as well.

Here’s why that’s important to security. Let’s say a hacker attempts to edit your transaction. As soon as they do that, the block’s hash will change. The next block in the chain will still contain the old hash, and the hacker would need to update that block in order to cover their tracks. However, doing so would change that block’s hash. In order to change a single block, a hacker would need to change every single block after it on the blockchain. Recalculating all those hashes would take an enormous and improbable amount of computing power. In other words, once a block is added to the blockchain it becomes very difficult to edit and impossible to delete.

What are “proof of work” and “mining”?

To address the issue of trust, blockchain networks have implemented tests for computers that want to join and add blocks to the chain. The tests, called “consensus models,” require users to “prove” themselves before they can participate in a blockchain network. One of the most common examples employed by Bitcoin is called “proof of work.”

In the proof of work system, computers must “prove” that they have done “work” by solving a complex computational math problem. If a computer works on it and solves it, it becomes eligible to add a block to the blockchain. But the process of adding blocks to the it, what the cryptocurrency world calls “mining,” is not easy. In fact, the odds of solving one of these problems on the Bitcoin network were about one in 15.5 trillion in January 2020.1 To solve complex math problems at those odds, computers must run programs that cost them significant amounts of power and energy.

What does “decentralized” mean?

When it comes to printed money, the use of printed currency is regulated and verified by a central authority, usually a bank or government—but Bitcoin is not controlled by anyone. Instead, transactions made in bitcoin are verified by a network of computers. This is what is meant by the Bitcoin network and blockchain being “decentralized.”

When one person pays another for goods using bitcoin, computers on the Bitcoin network race to verify the transaction. In order to do so, users run a program on their computers and try to solve a complex mathematical problem, called a “hash.” When a computer solves the problem by “hashing” a block, its algorithmic work will have also verified the block’s transactions. As we described above, the completed transaction is publicly recorded and stored as a block on the blockchain, at which point it becomes unalterable. In the case of Bitcoin, and most other blockchains, computers that successfully verify blocks are rewarded for their labor with cryptocurrency. This is commonly referred to as “mining.”

What are wallet, public key and private key?

Although transactions are publicly recorded on the blockchain, user data is not—or, at least not in full. In order to conduct transactions on the Bitcoin network, participants must run a program called a “wallet.” Each wallet consists of two unique and distinct cryptographic keys: a public key and a private key. The public key is the location where transactions are deposited to and withdrawn from. This is also the key that appears on the blockchain ledger as the user’s digital signature.

Even if a user receives a payment in bitcoins to their public key, they will not be able to withdraw them with the private counterpart. A user’s public key is a shortened version of their private key, created through a complicated mathematical algorithm. However, due to the complexity of this equation, it is almost impossible to reverse the process and generate a private key from a public key. For this reason, blockchain technology is considered confidential.

If you still have questions about how blockchain works, let us know.