CBSE Architectural and Design Security 2 — Questions and Answers
Question 1: In a permissioned blockchain architecture, which access control model is most appropriate for enforcing role-based restrictions on transaction submission?
- Discretionary Access Control (DAC)
- Mandatory Access Control (MAC)
- Role-Based Access Control (RBAC) (Correct answer)
- Attribute-Based Access Control (ABAC)
Correct answer: Role-Based Access Control (RBAC)
RBAC maps organizational roles directly to permitted transaction types, aligning with the structured membership model of permissioned blockchains.
Question 2: What cryptographic mechanism enables a node to prove it possesses a valid credential without revealing the credential itself during network authentication?
- Symmetric key exchange
- Zero-knowledge proof (Correct answer)
- Hash-based message authentication
- Threshold signature
Correct answer: Zero-knowledge proof
Zero-knowledge proofs let a prover convince a verifier of a statement's truth without disclosing the underlying secret.
Question 3: A blockchain design uses a separate chain for high-frequency micropayments that periodically settles to the main chain. This pattern is best described as:
- Sharding
- State channel / payment channel
- Cross-chain atomic swap
- Sidechain (Correct answer)
Correct answer: Sidechain
A sidechain runs independently with its own consensus and periodically anchors or transfers assets back to the main chain.
Question 4: Which threat does the 'nothing-at-stake' problem primarily affect in blockchain consensus design?
- Proof-of-Work mining centralization
- Proof-of-Stake validator equivocation (Correct answer)
- Byzantine fault tolerance threshold
- Sybil resistance in permissioned networks
Correct answer: Proof-of-Stake validator equivocation
In early Proof-of-Stake designs, validators faced no cost for signing multiple conflicting forks, enabling double-spend attacks without economic penalty.
Question 5: When designing a multi-signature wallet contract, what is the primary security risk of setting the required-signature threshold too low?
- Increased gas costs per transaction
- Reduced resistance to key compromise enabling unauthorized fund transfer (Correct answer)
- Slower block confirmation times
- Incompatibility with hardware wallets
Correct answer: Reduced resistance to key compromise enabling unauthorized fund transfer
A low threshold means compromising fewer keys is sufficient for an attacker to authorize transactions unilaterally.
Question 6: Which architectural principle is violated when a smart contract stores all application state on-chain, including data that never participates in consensus logic?
- Separation of concerns (Correct answer)
- Least privilege
- Defense in depth
- Fail-safe defaults
Correct answer: Separation of concerns
Separation of concerns is violated because on-chain storage should be limited to data requiring trustless consensus, not auxiliary application state.
Question 7: In Hyperledger Fabric, which component is responsible for ordering transactions into blocks before distributing them to peers?
- Endorsing peer
- Committing peer
- Ordering service (orderer) (Correct answer)
- Certificate Authority
Correct answer: Ordering service (orderer)
The ordering service collects endorsed transactions, sequences them deterministically, and cuts blocks for delivery to all channel peers.
CBSE Architectural and Design Security 2
In a permissioned blockchain architecture, which access control model is most appropriate for enforcing role-based restrictions on transaction submission?