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CBSA Certified Blockchain Solution Architect –
Practice Exam
Total Questions: 250 Question Type: Multiple Choice (A, B, C, D) Target Audience: Candidates preparing for the Certified Blockchain Solution Architect (CBSA) examination Answer Format: Correct answer + explanation immediately following each question This practice exam covers blockchain architecture, consensus mechanisms, cryptography, smart contracts, permissioned vs. permissionless networks, enterprise blockchain platforms (Ethereum, Hyperledger Fabric, Corda), security, privacy, tokenization, and integration with existing systems.
Topic 1: Blockchain Fundamentals & Architecture (Questions 1-
- What is the primary difference between a blockchain and a traditional distributed database? A) Blockchain uses a central server; distributed database uses multiple servers B) Blockchain is immutable and append-only with cryptographic linking; traditional databases support update/delete operations C) There is no difference D) Blockchain cannot be distributed Answer: B Explanation: Blockchain creates an immutable, append-only ledger where each block is cryptographically linked to the previous block. Traditional databases allow updates and deletions.
- Which of the following best describes a "block" in a blockchain? A) A single transaction B) A collection of transactions bundled with a header containing a timestamp, nonce, and hash of the previous block C) A smart contract D) A consensus algorithm Answer: B
C) Anonymity D) Speed Answer: B Explanation: Changing any block would change its hash, breaking the link to the next block, and would require re-mining all subsequent blocks (in proof-of-work systems).
- In a public permissionless blockchain, which of the following is true? A) Only authorized participants can read and write B) Anyone can read, write, and validate transactions (subject to consensus rules) C) Only the government can access D) Transactions are not validated Answer: B Explanation: Public permissionless blockchains (e.g., Bitcoin, Ethereum) allow anyone to join, read, submit transactions, and participate in consensus (validation).
- Which of the following is a characteristic of a permissioned (private) blockchain? A) Fully anonymous B) Access controlled by a central authority or consortium; participants are known and authorized C) No consensus mechanism needed D) Uses proof-of-work exclusively Answer: B Explanation: Permissioned blockchains restrict read/write/validate access to known, authorized participants (e.g., Hyperledger Fabric, Corda).
- What is the "blockchain trilemma" as described by Vitalik Buterin? A) Decentralization, security, scalability (can only achieve two of three) B) Privacy, transparency, speed C) Cost, speed, security D) Immutability, anonymity, finality Answer: A
Answer: B Explanation: Nodes maintain the blockchain copy, validate incoming transactions and blocks, and propagate data to peers.
- What is the difference between a full node and a light node? A) Full nodes store full blockchain history; light nodes store only block headers B) No difference C) Light nodes store full history D) Full nodes cannot validate transactions Answer: A Explanation: Full nodes download and verify every block. Light nodes download only block headers and request transaction proofs from full nodes when needed.
- Which consensus mechanism requires participants to stake cryptocurrency as collateral to validate transactions? A) Proof of Work (PoW) B) Proof of Stake (PoS)
C) Delegated Proof of Stake (DPoS) D) Proof of Authority (PoA) Answer: B Explanation: In Proof of Stake, validators lock (stake) cryptocurrency as collateral. Misbehavior results in slashing (loss of stake).
- What is the "51% attack" in proof-of-work blockchains? A) An attack where an entity controls more than 50% of mining hash rate, potentially double-spending or reorganizing blocks B) An attack on smart contracts C) A Denial-of-Service attack D) A wallet hack Answer: A Explanation: A 51% attack allows the attacker to reverse transactions (double-spend) and censor transactions by mining a private chain longer than the honest chain.
- What is a "fork" in blockchain? A) A tool for mining
- Which blockchain platform uses the UTXO (Unspent Transaction Output) model? A) Ethereum B) Bitcoin (and Cardano, Bitcoin Cash) C) Hyperledger Fabric D) Corda Answer: B Explanation: Bitcoin and many others use the UTXO model (inputs reference previous unspent outputs). Ethereum uses an account- based model.
- What is the difference between UTXO and account-based models? A) UTXO tracks individual coins; account-based tracks account balances like a bank B) No difference C) UTXO is only for permissioned chains D) Account-based is only for Bitcoin
Answer: A Explanation: UTXO treats each transaction output as a discrete coin; account-based (Ethereum) maintains a global state of account balances.
- What is "finality" in blockchain? A) The time it takes to mine a block B) The guarantee that a transaction will not be reversed (reorged) C) The block size limit D) The number of confirmations Answer: B Explanation: Finality means that once a transaction is included in a block, it is irreversible. Probabilistic finality (PoW) vs. deterministic finality (PoS, PBFT).
- Which consensus algorithm provides deterministic finality? A) Bitcoin PoW B) Practical Byzantine Fault Tolerance (PBFT) C) Ethereum PoW (pre-merge) D) Nakamoto consensus
C) A consensus failure D) A wallet vulnerability Answer: B Explanation: Blockchains are deterministic and cannot pull external data. Oracles provide off-chain data (e.g., price feeds) but introduce trust assumptions.
- Which of the following is an example of a decentralized oracle network? A) Infura B) Chainlink (decentralized oracles) C) MetaMask D) Truffle Answer: B Explanation: Chainlink is a decentralized network of nodes that fetch and verify external data for smart contracts.
- What is "sharding" as a scaling solution?
A) Splitting the blockchain into multiple parallel chains (shards), each processing transactions in parallel B) Increasing block size C) Reducing block time D) Using faster hardware Answer: A Explanation: Sharding divides the network into shards that process transactions in parallel, increasing throughput. Ethereum 2. implements sharding.
- In the context of blockchain, what does "nonce" mean? A) A random number used in proof-of-work mining to find a valid block hash B) A type of transaction C) A smart contract function D) A wallet address Answer: A Explanation: In PoW, miners vary the nonce to produce a hash below the target difficulty. In Ethereum accounts, nonce is transaction count.
Explanation: Block reward = coinbase reward (new coins, currently 3.125 BTC after 2024 halving) + transaction fees.
- What is the "halving" in Bitcoin? A) Reducing block time B) Reducing the block reward by 50% approximately every 4 years (210,000 blocks) C) Reducing transaction fees D) Reducing block size Answer: B Explanation: Halving reduces the coinbase reward, controlling supply inflation. Total supply capped at 21 million BTC.
- Which of the following is a privacy-focused blockchain? A) Bitcoin B) Monero (using ring signatures and stealth addresses) C) Ethereum D) Solana Answer: B
Explanation: Monero uses ring signatures, stealth addresses, and RingCT to obscure sender, receiver, and amount. Zcash uses zk- SNARKs.
- What is "transaction malleability" in Bitcoin? A) The ability to change transaction ID without invalidating the transaction, exploited in early Mt. Gox attacks B) The ability to reverse transactions C) The ability to double-spend D) The ability to censor transactions Answer: A Explanation: Transaction malleability allows changing the signature without invalidating the transaction, changing the txid. Segwit fixed this.
- What is the "gas" in Ethereum? A) A type of token B) A unit measuring computational effort required to execute transactions or smart contracts C) The block reward D) A consensus mechanism
D) To manage consensus Answer: B Explanation: The EVM is a stack-based virtual machine that executes smart contract bytecode across all Ethereum nodes, ensuring deterministic results.
- Which of the following is a key feature of the EVM? A) Non-deterministic execution B) Deterministic execution (same input always produces same output) C) Random number generation D) External API calls without oracles Answer: B Explanation: The EVM is deterministic to ensure all nodes reach the same state after executing transactions.
- What is a "self-destruct" function in an Ethereum smart contract? A) A bug
B) A function that removes the contract code from the blockchain and sends its remaining ETH balance to a specified address C) A function that locks the contract D) A consensus rule Answer: B Explanation: selfdestruct(address) removes the contract code and sends all remaining ETH to the target address. It was renamed to withdraw in newer versions.
- What is "non-deterministic" behavior in a smart contract? A) Behavior that depends on external state (e.g., block timestamp, blockhash, randomness) or off-chain data B) Always same output C) Deterministic randomness D) Contract upgrade Answer: A Explanation: Smart contracts should be deterministic, but certain values (block.timestamp, blockhash) are pseudo-random and can be manipulated by miners.
