CBSA Solution Architecture Design 5 — Questions and Answers
Question 1: A blockchain architect is designing a decentralized identity (DID) solution. Which W3C standard defines the core data model for self-sovereign identity?
- OAuth 2.0 with blockchain extension
- Decentralized Identifiers (DIDs) W3C specification (Correct answer)
- OpenID Connect with NFT binding
- X.509 certificates stored on-chain
Correct answer: Decentralized Identifiers (DIDs) W3C specification
The W3C DID specification defines a standard data model for decentralized identifiers that are globally unique, resolvable, and cryptographically verifiable without a central registry.
Question 2: When designing a blockchain governance model, which mechanism best prevents plutocratic control (wealthy actors dominating decisions)?
- Token-weighted voting with a maximum cap
- Quadratic voting where cost increases with vote count (Correct answer)
- Delegation to elected council members
- One-token-one-vote with quorum requirements
Correct answer: Quadratic voting where cost increases with vote count
Quadratic voting makes each additional vote on the same issue progressively more expensive, reducing the outsized influence of large token holders while preserving minority voice.
Question 3: A CBSA architect is designing a blockchain solution for carbon credit trading. Which on-chain data element is most essential for preventing double-spending of credits?
- The carbon offset project description
- A unique serial number with spent/unspent state tracking (Correct answer)
- The verifier's digital signature only
- The transaction timestamp
Correct answer: A unique serial number with spent/unspent state tracking
Each carbon credit must have a unique serial number with a tracked state (issued, transferred, retired) on-chain to ensure a credit can only be used to offset emissions once.
Question 4: In a multi-party computation (MPC) wallet architecture for enterprise blockchain, what is the primary security advantage over a traditional single private key?
- Faster transaction signing speed
- No single point of compromise — key shares are distributed across parties (Correct answer)
- Reduced gas costs for transactions
- Compatibility with all blockchain protocols
Correct answer: No single point of compromise — key shares are distributed across parties
MPC distributes key shares among multiple parties such that no single compromised party can reconstruct the private key or sign transactions unilaterally, eliminating the single point of failure.
Question 5: An architect is designing a blockchain system that must maintain high availability during a network partition. According to the CAP theorem, which two properties does a blockchain system typically prioritize?
- Consistency and Availability
- Availability and Partition tolerance
- Consistency and Partition tolerance (Correct answer)
- All three equally
Correct answer: Consistency and Partition tolerance
Most blockchain systems prioritize Consistency (all nodes see the same ledger state) and Partition tolerance (network continues operating during partitions), sacrificing some Availability during splits.
Question 6: Which architectural pattern is most effective for managing secret data (API keys, credentials) that smart contracts need to access external services?
- Hardcoding secrets in smart contract bytecode
- Trusted Execution Environment (TEE) with encrypted oracle delivery (Correct answer)
- Storing secrets in IPFS with access control
- Using environment variables in the EVM
Correct answer: Trusted Execution Environment (TEE) with encrypted oracle delivery
TEE-based oracles (like those used by Chainlink DECO or Town Crier) execute in secure enclaves that provide cryptographic attestation, delivering secrets to smart contracts without exposing them on-chain.
Question 7: When architecting a blockchain solution that requires deterministic execution across all nodes, why are timestamps from block headers unreliable for time-sensitive logic?
- Block headers do not contain timestamps
- Miners/validators can manipulate timestamps within a tolerance window (Correct answer)
- Timestamps are stored off-chain and must be fetched via oracles
- Block timestamp precision is limited to whole days
Correct answer: Miners/validators can manipulate timestamps within a tolerance window
Block producers can set timestamps within an allowed drift range (e.g., ±15 seconds on Ethereum), creating a manipulation vector for contracts with time-sensitive logic like expiry conditions.
CBSA Solution Architecture Design 5
A blockchain architect is designing a decentralized identity (DID) solution.
Which W3C standard defines the core data model for self-sovereign identity?