Byzantine Fault Tolerant (BFT) Mechanisms BDC Practice Questions (Page 6)

Questions 26–30

1. 26foundation · medium

   Which of the following is a characteristic of the Tendermint consensus algorithm?

   • AIt relies on a Byzantine fault-tolerant state machine replication with a rotating proposer.
   • BIt requires a minimum of 2f+1 nodes to tolerate f Byzantine faults.
   • CIt uses a leaderless approach where all nodes propose blocks simultaneously.
   • DIt is designed for permissionless networks with no identity requirements.
   Reveal Solution Discussion Select an answer first
2. 27foundation · medium

   What is a major scalability limitation of traditional BFT algorithms like PBFT?

   • AThey require a central authority to coordinate consensus.
   • BThey cannot handle more than 100 nodes in the network.
   • CThey are vulnerable to Sybil attacks because they do not require node identities.
   • DThey require all nodes to communicate with each other, leading to O(n^2) message complexity.
   Reveal Solution Discussion Select an answer first
4. 28expert · hard

   A fintech company is building a permissioned blockchain for cross-border payments. They have 21 validator nodes. Requirements: (1) finality in under 2 seconds, (2) tolerate up to 5 Byzantine validators, (3) minimize communication overhead, (4) operate in a partially synchronous network. They are considering PBFT, Tendermint, and HotStuff. Which protocol best meets all requirements?

   • AHotStuff
   • BTendermint
   • CRaft
   • DPBFT
   Reveal Solution Discussion Select an answer first
5. 29foundation · medium

   What type of failure does crash fault tolerance (CFT) specifically address?

   • ANodes that are compromised by an attacker and act maliciously.
   • BNodes that stop responding or crash permanently.
   • CNodes that are slow but eventually respond.
   • DNodes that send conflicting messages to different parts of the network.
   Reveal Solution Discussion Select an answer first
6. 30application · medium

   A developer is debugging a PBFT network with 4 nodes. The primary node sends a pre-prepare for a new block. One replica receives the pre-prepare but the network is partitioned, so it cannot communicate with the other two replicas for a short period. What is the impact on the replica's ability to proceed?

   • AIt can proceed because the primary's pre-prepare is sufficient
   • BIt cannot proceed because it cannot collect the required 2f+1 prepare messages
   • CIt can proceed by using the commit phase directly
   • DIt can proceed because it only needs its own prepare message
   Reveal Solution Discussion Select an answer first