How Does Blockchain Work?

3 min read

A blockchain is a decentralized database technology that stores data in blocks that are appended linearly. New blocks are added to the end, and the data remains practically immutable through cryptographic processes – any manipulation becomes immediately apparent [1]. In principle, the block chain can be compared to a written cash book or ledger in which all transactions are written down from day one [8]. One can also imagine a blockchain as a publicly viewable digital register in which something can be entered, but can hardly be changed afterwards [9]. It functions as a continuously expandable chain of data blocks and forms the backbone of cryptocurrencies such as Bitcoin [4] [5].

Structure: Blocks and Hash Functions

A blockchain works like a continuous, digitally secured chain of data blocks. Transactions are bundled, verified, linked, and stored decentrally [3]. Each block contains transaction data, a timestamp, and links cryptographically to the previous block – typically via its hash [4]. A hash function converts any data into a fixed, unique code. Even a minimal change produces a completely different hash, and the process is irreversible. This creates an immutable chain: if a block is manipulated, all subsequent hashes no longer match.

Decentralization and Consensus

A consensus mechanism ensures that all computers in the network agree on the current state of the block chain [1]. Due to the linked structure and decentralized consensus, subsequent modification of data is made difficult, as it would compromise the integrity of the entire system. Thus, decentralized consensus replaces the need for a trusted third party to confirm transactions [4].

Proof of Work and Proof of Stake

New blocks are created and appended to the chain via consensus mechanisms [4]. The best-known public blockchains, such as Bitcoin or Ethereum, are publicly accessible and generally based on the Proof-of-Work process [2]. In Proof of Work (PoW), miners solve complex computational puzzles with high energy consumption to create blocks – the fastest wins the reward. In Proof of Stake (PoS), on the other hand, validators stake cryptocurrency as collateral; blocks are selected randomly based on the stake, and manipulation leads to the loss of the stake. PoW is considered very secure but is power-hungry, while PoS is more energy-efficient and environmentally friendly. In addition to these two methods, there are many other consensus mechanisms such as Proof of Space, Proof of Burn, Proof of Activity, and Proof of History [4].

Applications Beyond Cryptocurrencies

Blockchain technology has attracted a lot of attention in recent years, particularly in connection with Bitcoin and other cryptocurrencies [7]. However, it is not only revolutionizing the financial world but is also finding application in numerous other areas. Other applications include supply chain tracking for the seamless and tamper-proof tracking of products, smart contracts for automated agreements, decentralized identity solutions, secure voting systems, and the storage of medical data.

Limits and Risks

Although blockchain technology is considered one of the greatest innovations of the internet age [6], it also brings challenges. Technical limits include scalability issues with slow transactions, high energy consumption in Proof of Work, and a continuously growing amount of data. In the area of security and implementation, immutability makes it difficult to correct errors; furthermore, risks exist due to smart contract vulnerabilities and potential 51 percent attacks. Additional risks include regulatory uncertainty, loss of keys, data protection issues in terms of the GDPR, and a lack of interoperability between different blockchains.