What Is Blockchain? | IT Passport Exam Prep | Mechanisms, Uses, and Smart Contracts

What Is Blockchain?

Blockchain is a distributed ledger technology that groups transaction data into "blocks" and links them together in a chain using hash values of the previous block. It requires no central administrator, and because many nodes share the same ledger, tampering is extremely difficult. This technology was originally conceived as the foundation for Bitcoin, proposed in a 2008 paper by Satoshi Nakamoto.

Why Is Tampering So Difficult?

Each block contains the "hash value of the previous block," so if one block is altered, the hash values of all subsequent blocks change in a chain reaction. This makes tampering detectable. Furthermore, successfully tampering would require taking over a majority of the nodes—an attack known as a 51% attack. For more on hash functions, see Encryption Basics.

Consensus Algorithms

PoW (Proof of Work) is a method where the node that solves a massive computational puzzle first gets to add a new block; it is used by Bitcoin. However, it has the drawback of high power consumption. In contrast, PoS (Proof of Stake) favors nodes with larger holdings of cryptocurrency for block generation, operating with much lower energy use. Ethereum switched to PoS in 2022.

Major Applications

Cryptocurrency

Bitcoin and Ethereum are well-known cryptocurrencies. Unlike fiat currency, they are not issued by a central bank, and transactions are managed on the blockchain.

Smart Contracts

Smart contracts are programs that execute automatically on the blockchain. When predefined conditions are met, transactions are carried out automatically. Ethereum is the most prominent example, and it also serves as the foundation for DeFi (decentralized finance) and NFTs.

NFT (Non-Fungible Token)

NFTs, or non-fungible tokens, are a mechanism for proving the uniqueness of a digital asset. They are used in various fields, including digital art, in-game items, and membership rights.

Supply Chain Management

Production histories of food or distribution routes of pharmaceuticals can be recorded in a tamper-proof manner. This is expected to improve traceability.

Key Points for the IT Passport Exam

Frequent topics include the basic structure of blockchain—distributed ledger, hash chain, and tamper resistance. You will also need to identify terms such as smart contracts, NFTs, and cryptocurrencies. Questions often compare blockchain with centralized databases, so be sure to understand the differences.

Typical Past Exam Question Patterns

• "Which of the following best describes a characteristic of blockchain?"
• "Which of the following is a correct description of a smart contract?"

Related Terms

• Hash functions and public-key cryptography (Encryption Basics)
• Financial service transformation in the context of DX (What Is DX?)

Study Tips

Memorize the core trio: "block + hash chain + distributed ledger." To understand the difference between PoW and PoS, compare them as "computational power" vs. "stake amount." Think of smart contracts and NFTs as "applications on the blockchain."

Summary

If you master the mechanism (hash chain), consensus (PoW/PoS), and major applications, you can score well on related exam questions. For comprehensive practice in the Technology domain, check out the Technology Category Summary. To challenge yourself with a full-length practice test, try the Mock Exam.