Consensus Mechanism Vulnerabilities Flashcards
7 cards from real Blockchain Technology practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Consensus Mechanism Vulnerabilities flashcards as text
A Sybil attack against a consensus network involves:
Answer: One entity creating many fake identities/nodes to gain disproportionate influence
Sybil attacks spawn numerous fake identities; consensus mechanisms resist them by tying influence to a scarce resource like hash power or stake.
How do Proof-of-Work and Proof-of-Stake fundamentally resist Sybil attacks?
Answer: By making influence proportional to a costly resource rather than node count
Both tie voting weight to scarce resources (computation or capital), so spinning up many identities provides no advantage without proportional cost.
An 'eclipse attack' isolates a node by:
Answer: Monopolizing its peer connections so it only sees attacker-controlled information
By controlling all of a victim node's peer connections, the attacker feeds it a manipulated view of the blockchain, enabling double-spends or wasted mining.
Practical Byzantine Fault Tolerance (PBFT) can tolerate faulty nodes up to what fraction?
Answer: Fewer than one-third of nodes
BFT consensus remains safe and live only if fewer than one-third of participants are Byzantine (malicious or faulty).
A 'liveness failure' in a consensus protocol means:
Answer: The network stops making progress / finalizing new transactions
Liveness failure is a halt in progress; safety failure is conflicting/invalid state, and BFT designs often trade one for the other under attack.
Why is peer-discovery diversity important for resisting eclipse attacks?
Answer: Connecting to many independent, hard-to-predict peers makes monopolizing connections difficult
Diverse, randomized peer selection prevents an attacker from occupying all of a node's connection slots and controlling its view.
A consensus mechanism that prioritizes 'safety over liveness' will, under severe network partition:
Answer: Halt finalization rather than risk conflicting confirmed states
Safety-favoring protocols stop finalizing during partitions to avoid two conflicting histories, accepting a temporary halt instead.