Blockchain Fundamentals & Architecture Flashcards

What is the primary difference between Layer 1 and Layer 2 blockchain solutions?

Answer: Layer 1 refers to the base blockchain protocol; Layer 2 refers to solutions built on top to improve scalability

Layer 1 is the base chain (Bitcoin, Ethereum) with its own consensus and security; Layer 2 solutions (Lightning, Rollups) extend L1 capacity by processing transactions off-chain while inheriting L1 security.

What is a 'zero-knowledge proof' and how is it used in blockchain?

Answer: A cryptographic method allowing one party to prove knowledge of information without revealing the information itself

Zero-knowledge proofs (e.g., zk-SNARKs) let a prover demonstrate a statement is true (e.g., 'I have enough balance') without revealing the underlying data, enabling privacy and efficient rollups.

In blockchain architecture, what is the 'Byzantine Generals Problem' and why is it relevant?

Answer: A distributed computing problem describing how decentralized nodes can reach consensus despite some acting maliciously

The Byzantine Generals Problem describes the challenge of achieving reliable consensus in a distributed system where some participants may be faulty or malicious — solving it is the core challenge of blockchain consensus.

What does 'immutability' mean in the context of a public blockchain?

Answer: Once confirmed with sufficient depth, data on the chain is practically impossible to alter without redoing all subsequent proof-of-work

Blockchain immutability means that altering a historical transaction would require redoing the proof-of-work (or stake) for that block and all blocks after it, making it economically infeasible on large networks.

What is the 'double-spend problem' and how does blockchain solve it without a central authority?

Answer: The risk of spending the same digital token twice; solved by distributed consensus that orders transactions globally

Without a central ledger, digital money can be copied and spent twice; blockchain solves this by having the entire network agree on a single ordered transaction history, making double-spends visible and rejectable.

What is a 'hard fork' in blockchain and what are its consequences?

Answer: A non-backward-compatible protocol change that creates two separate incompatible chains if not all nodes upgrade

A hard fork introduces rules that old nodes reject, so unupgraded nodes continue on the old chain while upgraded nodes follow the new rules, potentially creating two permanent chains (e.g., ETH/ETC split after The DAO hack).

What is the purpose of the 'gas' mechanism in Ethereum's blockchain architecture?

Answer: To meter computational work done by the EVM, preventing infinite loops and spam while compensating validators

Gas assigns a computational cost to every EVM operation; users pay gas fees (in ETH) to compensate validators and the system rejects transactions that exceed the gas limit, preventing denial-of-service via infinite loops.