CBSA Sample Questions & Answers
Expect questions on blockchain history and core terminology, proof systems and Byzantine fault tolerance, how different blockchain types and tokenomics compare, cryptographic foundations, and choosing and deploying a solution architecture.
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- Question 1Advanced
Cryptography and Security · Zero-Knowledge Proofs
While designing a private blockchain for a healthcare consortium, an architect needs to ensure that patient data remains confidential and is not revealed on the ledger, but its integrity must be verifiable by auditors. Which cryptographic technique allows a party to prove that a statement is true (e.g., 'this medical record has not been altered') without revealing any information beyond the validity of the statement itself?
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Correct answer: C
Zero-Knowledge Proofs (ZKPs) are a class of cryptographic protocols that enable one party (the prover) to prove to another party (the verifier) that a statement is true, without revealing any information other than the fact that the statement is indeed true. This is perfect for the healthcare use case, as the integrity of the patient data can be proven on-chain without exposing the confidential data itself.
- Question 2IntermediateSelect 2
Consensus Mechanisms and Proof Systems · Delegated Proof of Stake (DPoS)
A solution architect is comparing Delegated Proof of Stake (DPoS) with standard Proof of Stake (PoS) for a new social media platform that requires high throughput and fast block confirmation times. What are the key architectural trade-offs when choosing DPoS over PoS? (Select TWO)
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Correct answers: A, D
DPoS achieves higher throughput by reducing the number of block-producing nodes (witnesses/delegates) to a small, fixed set, enabling faster consensus.
The primary trade-off for the performance gains in DPoS is a reduction in decentralization, as a small number of elected entities are responsible for running the network.
- Question 3Beginner
Blockchain Types and Classifications · Token Standards
A government agency is building a land registry system on a blockchain. They want to issue a unique, non-interchangeable digital token for each parcel of land. These tokens must be transferable and have a clear, verifiable ownership history on-chain. Which Ethereum token standard should the architect specify for this use case?
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Correct answer: B
The ERC-721 standard is the correct choice as it defines non-fungible tokens (NFTs). Each token is unique and not interchangeable, making it perfect for representing one-of-a-kind assets like parcels of land. ERC-20 is for fungible tokens (like a cryptocurrency), ERC-1155 is a multi-token standard, and ERC-777 is an advanced fungible token standard.
- Question 4Advanced
Cryptography and Security · Cross-Chain Security
During the design of a cross-chain bridge, a security architect raises a concern about the risks associated with the 'lock-and-mint' mechanism. What is the primary security vulnerability inherent in many lock-and-mint bridge designs?
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Correct answer: B
The primary vulnerability in lock-and-mint bridges is the large pool of assets locked in the source chain's smart contract. This contract becomes a high-value target for hackers. If the contract is exploited, the locked assets can be stolen, while the 'wrapped' or minted assets on the destination chain become unbacked and worthless. This honeypot effect has been the cause of numerous major DeFi hacks.
- Question 5Intermediate
Consensus Mechanisms and Proof Systems · Crash Fault Tolerance
A solution architect is evaluating blockchain platforms for an enterprise use case that requires strict transaction ordering and finality, but does NOT need to tolerate malicious (Byzantine) actors within its permissioned set of nodes. The primary goal is to prevent inconsistencies due to network partitions or node crashes. Which type of consensus algorithm would be most appropriate and efficient?
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Correct answer: C
Crash Fault Tolerant (CFT) algorithms, like Raft, are designed to maintain consensus in systems where nodes may fail by crashing or going offline, but are assumed not to be malicious. Since the requirement explicitly states the system does not need to tolerate Byzantine actors, a CFT consensus mechanism is more efficient and less complex than a BFT one, making it the most appropriate choice.
- Question 6Intermediate
Cryptography and Security · Digital Signatures
A university is developing a system to issue academic credentials on a public blockchain. To ensure authenticity and prevent forgery, each diploma must be digitally signed by the university's registrar. Which of the following describes the correct cryptographic process for this?
sequenceDiagram participant Registrar participant DiplomaData participant Blockchain Registrar->>DiplomaData: Hash(Diploma Details) Registrar->>Registrar: Sign(Hash) with Private Key Registrar->>Blockchain: Store (Diploma Details, Signature) participant Verifier Blockchain-->>Verifier: Retrieve (Diploma, Signature) Verifier->>DiplomaData: Hash(Diploma Details) Verifier->>Verifier: Verify(Signature, Hash, Registrar's Public Key) --> bool ResultShow answer & explanation
Correct answer: C
This is the correct process for creating a digital signature. Hashing the data creates a unique, fixed-size fingerprint. Signing this hash with the registrar's private key proves that they are the one who created the signature. Anyone can then use the publicly available registrar's public key to verify that the signature is valid for that specific diploma hash, confirming authenticity and integrity without needing access to the private key.
- Question 7Beginner
Blockchain Fundamentals and Architecture · Core Blockchain Components
The genesis block of a blockchain is unique because it is the only block in the chain that does not have a ____.
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Correct answer: C
The genesis block is the first block of a blockchain. Since there are no blocks before it, it is the only block that does not contain a reference (hash) to a previous block. This is what establishes the beginning of the chain.
- Question 8Intermediate
Blockchain Types and Classifications · Token Standards
An architect is designing a system for managing fractional ownership of real estate. The system must support both unique property deeds (as individual assets) and fungible tokens representing shares in a property. The solution should be implemented on an Ethereum-compatible chain. Which token standard provides the most efficient and standardized way to manage both fungible and non-fungible tokens within a single smart contract?
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Correct answer: B
ERC-1155 is the multi-token standard that allows for the creation of both fungible and non-fungible tokens within a single contract. This is highly efficient for the described use case, as a single contract could manage the unique NFT for the property deed (balance of 1) and the multiple fungible tokens for ownership shares (balance > 1). This reduces deployment costs and simplifies token management.
- Question 9Beginner
Blockchain Types and Classifications · Blockchain Use Cases
A blockchain solution is being developed to track ethical sourcing of diamonds, from mine to retailer. The solution requires a high degree of privacy, control over participants, and high transaction throughput. The participants (mining companies, certifiers, distributors) are known and trusted entities. Which type of blockchain architecture is most suitable for this use case?
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Correct answer: B
A private/permissioned blockchain is the best fit. The requirements for privacy, participant control (only known entities can join), and high throughput are characteristic of enterprise use cases that are not suitable for a public blockchain. Platforms like Hyperledger Fabric or R3 Corda are designed for such consortium models.
- Question 10Advanced
Cryptography and Security · Privacy Enhancing Technologies
A solution architect must design a system that allows for private transactions on a public, Ethereum-based blockchain. The goal is to obscure the sender, receiver, and amount for specific transactions to protect user privacy. Which technology would be most appropriate to integrate into the solution to achieve this?
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Correct answer: C
Protocols like Tornado Cash use Zero-Knowledge Succinct Non-Interactive Arguments of Knowledge (zk-SNARKs) to enable private transactions on public blockchains. A user deposits funds into a smart contract and can later withdraw them to a different address without creating a link between the deposit and withdrawal on-chain. The zk-SNARK proves that the user has the right to withdraw funds without revealing which deposit corresponds to the withdrawal, effectively breaking the transaction graph and providing privacy.
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