CBSA Core Blockchain Principles 5 — Questions and Answers
Question 1: What is a 'double-spend attack' and how does blockchain consensus prevent it?
- Paying twice the required gas fee; prevented by fee caps
- Attempting to spend the same digital asset twice; prevented by network-wide consensus validating transaction order (Correct answer)
- Deploying two identical smart contracts; prevented by address uniqueness
- Mining two blocks simultaneously; prevented by difficulty adjustment
Correct answer: Attempting to spend the same digital asset twice; prevented by network-wide consensus validating transaction order
Consensus ensures all nodes agree on a single transaction history, making it computationally or economically infeasible to retroactively alter confirmed transactions.
Question 2: In the context of blockchain scalability, what is a 'Layer 2 solution'?
- A second blockchain running in parallel with no connection to Layer 1
- A protocol built on top of a base blockchain that processes transactions off-chain and settles results on-chain (Correct answer)
- A hardware acceleration layer for mining
- A regulatory compliance layer added by governments
Correct answer: A protocol built on top of a base blockchain that processes transactions off-chain and settles results on-chain
Layer 2 solutions like Lightning Network or Optimistic Rollups handle transaction volume off the main chain, reducing congestion while inheriting Layer 1 security.
Question 3: What is 'chain reorganization' (reorg) and when does it occur?
- Manual reordering of transactions by miners for profit
- A network event where a longer competing chain replaces the current canonical chain (Correct answer)
- Scheduled block number resets for protocol upgrades
- Compressing old blocks to save storage space
Correct answer: A network event where a longer competing chain replaces the current canonical chain
Reorgs happen when two miners find valid blocks simultaneously; the network eventually adopts the chain with more accumulated work, orphaning the shorter branch.
Question 4: Which feature of zero-knowledge proofs makes them valuable for blockchain privacy solutions?
- They delete transaction history after verification
- They allow one party to prove knowledge of information without revealing the information itself (Correct answer)
- They prevent validators from reading transaction amounts
- They encrypt the entire blockchain ledger
Correct answer: They allow one party to prove knowledge of information without revealing the information itself
ZK proofs enable transaction validity to be verified without disclosing the underlying data, enabling privacy-preserving yet auditable blockchain transactions.
Question 5: What is the purpose of a 'mempool' (memory pool) in a blockchain network?
- Long-term archival storage for confirmed blocks
- A temporary holding area for broadcast but unconfirmed transactions awaiting inclusion in a block (Correct answer)
- RAM allocated to running smart contracts
- A cache storing the UTXO set
Correct answer: A temporary holding area for broadcast but unconfirmed transactions awaiting inclusion in a block
The mempool is a node-level queue where pending transactions wait; miners/validators select from it when building the next block, typically prioritizing higher-fee transactions.
Question 6: In a Delegated Proof of Stake (DPoS) system, what role do 'delegates' or 'witnesses' play?
- They audit smart contract code before deployment
- They are elected representatives who produce blocks on behalf of token holders who voted for them (Correct answer)
- They bridge assets between different blockchain networks
- They manage private key recovery for lost wallets
Correct answer: They are elected representatives who produce blocks on behalf of token holders who voted for them
DPoS delegates are voted in by stakeholders and take turns producing blocks, enabling faster consensus while maintaining some decentralization via democratic election.
Question 7: What is 'interoperability' in blockchain architecture and why is it a design challenge?
- The ability of a blockchain to run on multiple operating systems
- The capacity for different blockchain networks to communicate, share data, and transfer assets across chains (Correct answer)
- Ensuring smart contracts work on both testnet and mainnet
- Making blockchain data readable by traditional databases
Correct answer: The capacity for different blockchain networks to communicate, share data, and transfer assets across chains
Interoperability is challenging because different blockchains have incompatible protocols, consensus mechanisms, and data formats, requiring bridges, relays, or cross-chain protocols.
CBSA Core Blockchain Principles 5
What is a 'double-spend attack' and how does blockchain consensus prevent it?