CBSE Blockchain Threat Modeling 3 — Questions and Answers
Question 1: In a blockchain threat model, which data flow diagram (DFD) element represents the PostgreSQL database storing off-chain transaction metadata?
- Process
- External entity
- Data store (Correct answer)
- Trust boundary
Correct answer: Data store
A data store in a DFD represents any persistent storage system, such as a database holding off-chain metadata.
Question 2: Which blockchain-specific threat involves an attacker deliberately delaying block propagation to increase the chance that their competing block is accepted?
- Eclipse attack
- Selfish mining (Correct answer)
- Long-range attack
- Grinding attack
Correct answer: Selfish mining
Selfish mining withholds discovered blocks to gain a disproportionate share of block rewards by forcing honest miners to waste work on orphaned chains.
Question 3: A threat model for a cross-chain bridge identifies that the bridge's multi-sig wallet requires only 2-of-5 signers. What threat does this primarily expose?
- Denial of service via key exhaustion
- Threshold compromise allowing unauthorized fund transfers with only 2 colluding signers (Correct answer)
- Replay attacks across chains
- Reentrancy in the bridge smart contract
Correct answer: Threshold compromise allowing unauthorized fund transfers with only 2 colluding signers
A low threshold means only 2 signers need to be compromised or collude for an attacker to authorize fraudulent cross-chain transfers.
Question 4: Which LINDDUN privacy threat category is most relevant when a blockchain's transaction graph allows de-anonymization of user identities?
- Linkability (Correct answer)
- Non-repudiation
- Unawareness
- Detectability
Correct answer: Linkability
Linkability in LINDDUN describes the ability to correlate transactions or identities across a system, enabling de-anonymization in transparent blockchains.
Question 5: In threat modeling a smart contract upgrade proxy pattern, what is the primary security concern introduced by the upgradeability mechanism?
- Increased gas consumption during execution
- An unauthorized party could replace contract logic to drain funds or change behavior (Correct answer)
- The proxy pattern breaks ERC-20 token compatibility
- Upgradeability prevents formal verification of the contract
Correct answer: An unauthorized party could replace contract logic to drain funds or change behavior
If the upgrade authorization is misconfigured or compromised, an attacker can swap in malicious logic, undermining the immutability assumption of deployed contracts.
Question 6: A threat modeler identifies that validators in a PoS network can be bribed to sign conflicting blocks. Which countermeasure is specifically designed to deter this threat?
- Increasing block size limits
- Slashing conditions that penalize validators for equivocation (Correct answer)
- Adding more validator nodes to the network
- Implementing zero-knowledge proofs for transaction validation
Correct answer: Slashing conditions that penalize validators for equivocation
Slashing destroys a portion of a validator's staked collateral when they sign conflicting blocks, making equivocation economically irrational.
Question 7: When applying PASTA threat modeling to a blockchain application, which phase involves simulating realistic attack scenarios using threat intelligence?
- Phase 2 – Define Technical Scope
- Phase 5 – Vulnerability and Weakness Analysis
- Phase 6 – Attack Enumeration and Modeling (Correct answer)
- Phase 7 – Risk and Impact Analysis
Correct answer: Phase 6 – Attack Enumeration and Modeling
Phase 6 of PASTA focuses on enumerating and simulating attacker-centric scenarios using threat intelligence to model how identified weaknesses could be exploited.
CBSE Blockchain Threat Modeling 3
In a blockchain threat model, which data flow diagram (DFD) element represents the PostgreSQL database storing off-chain transaction metadata?