Architectural and Design Security Flashcards

In a Merkle tree-based blockchain, which security property allows a lightweight client to verify transaction inclusion without downloading the full ledger?

Answer: Merkle proof (SPV proof) against the block's Merkle root

A Merkle inclusion proof provides a logarithmic-length path from a transaction to the block's Merkle root, enabling Simplified Payment Verification (SPV) without the full chain.

What is the primary design risk of using a single externally owned account (EOA) as the owner of a critical protocol contract on a public blockchain?

Answer: Single private key compromise results in total protocol control loss

A single-key owner creates a critical single point of failure; compromise of that one key grants an attacker complete administrative control over the protocol.

Which consensus property is sacrificed when a blockchain network prioritizes availability and partition tolerance according to the CAP theorem?

Answer: Safety (consistency)

Per CAP theorem, choosing availability and partition tolerance means the system may return stale or conflicting state, sacrificing strong consistency (safety).

A blockchain architect wants to ensure that even the infrastructure provider cannot read stored contract state. Which technique best achieves confidential smart contract execution?

Answer: Trusted Execution Environments (TEE) such as Intel SGX for contract computation

TEEs provide hardware-enforced enclaves where code executes and state remains encrypted even from the host operating system and infrastructure provider.

What design flaw makes 'timestamp dependency' a security vulnerability in smart contracts?

Answer: Miners can adjust block timestamps within protocol tolerance to influence timestamp-dependent outcomes

Ethereum allows miners to set block.timestamp within a ~900-second window, enabling manipulation of time-sensitive contract logic like lottery draws or expiry checks.

Which architectural pattern ensures that a blockchain network can continue operating and reaching consensus even when a minority of validator nodes go offline simultaneously?

Answer: Byzantine Fault Tolerant protocol with liveness under (n - f) > 2f honest nodes

BFT protocols guarantee liveness as long as more than two-thirds of nodes are honest and responsive, so a minority outage does not halt the network.

In a token-curated registry (TCR) implemented as a smart contract, which governance attack involves an adversary accumulating a majority of voting tokens to control list inclusion decisions?

Answer: Plutocracy / token concentration attack

Token concentration allows a wealthy adversary to dominate votes on which entries are included or excluded, centralizing control of a supposedly decentralized registry.