Blockchain Fundamentals Flashcards

What is a 51% attack in blockchain networks?

Answer: When an entity controls the majority of network hash rate and can double-spend

A 51% attack occurs when a single miner or pool controls over half the hash rate, enabling them to rewrite recent blocks and potentially double-spend coins.

Which data structure does a blockchain most closely resemble?

Answer: Singly linked list

A blockchain is structurally a linked list where each block contains a cryptographic reference (hash) to its predecessor.

What is 'sharding' designed to solve in blockchain systems?

Answer: Scalability bottlenecks by partitioning the network into parallel subsets

Sharding splits the blockchain network into smaller partitions (shards) that process transactions in parallel, increasing overall throughput.

In proof-of-stake consensus, what primarily determines a validator's chance of proposing the next block?

Answer: The amount of cryptocurrency the validator has staked

In PoS, validators are selected to propose blocks proportionally to the amount of cryptocurrency they have locked as collateral (stake).

What is a blockchain 'oracle'?

Answer: A service that feeds real-world data to on-chain smart contracts

Oracles bridge the gap between blockchains and external data sources, supplying smart contracts with off-chain information like prices or event outcomes.

What is the purpose of the 'difficulty adjustment' mechanism in Bitcoin?

Answer: To keep average block production time near 10 minutes despite changing hash rate

Bitcoin recalculates mining difficulty every 2016 blocks to maintain an approximately 10-minute block interval regardless of total network hash power.

Which property ensures that altering any block in a blockchain invalidates all subsequent blocks?

Answer: Each block's hash is included in the next block's header

Because each block header contains the previous block's hash, modifying one block changes its hash and breaks the chain link to every following block.