Proof of Work (PoW) and Its Variations BDC Practice Questions (Page 3)

Questions 11–15

1. 11application · medium

   A blockchain startup is evaluating PoW for a public network. The CTO is concerned about a malicious actor creating thousands of fake nodes to dominate the network. Which property of PoW directly mitigates this specific threat?

   • AEach node is required to hold a minimum balance of the native token.
   • BThe network automatically bans nodes that produce invalid blocks.
   • CThe cost of obtaining voting power is tied to computational work, not the number of nodes.
   • DThe difficulty adjustment ensures that all nodes have equal hashing power.
   Reveal Solution Discussion Select an answer first
2. 12application · medium

   A blockchain network has a target block time of 2 minutes. Due to a sudden influx of miners, blocks are now being found every 30 seconds. What will happen at the next difficulty adjustment?

   • AThe difficulty will decrease, making it easier to find blocks, which will slow down block production.
   • BThe difficulty will remain the same because the target block time is fixed.
   • CThe block reward will be reduced to discourage miners, which will slow down block production.
   • DThe difficulty will increase, making it harder to find blocks, which will slow down block production back toward the target.
   Reveal Solution Discussion Select an answer first
4. 13expert · hard

   A blockchain project is under pressure from environmental groups to reduce its carbon footprint. The project currently uses PoW. The team is considering switching to PoS. Which trade-off must they carefully evaluate?

   • APoS requires specialized hardware, which increases the barrier to entry for validators.
   • BPoS reduces energy consumption but may lead to centralization because validators with larger stakes have more influence.
   • CPoS increases energy consumption but provides stronger security against 51% attacks.
   • DPoS eliminates the need for validators, so the network becomes fully decentralized.
   Reveal Solution Discussion Select an answer first
5. 14foundation · easy

   How does Proof of Work help prevent a Sybil attack on a blockchain network?

   • ABy requiring each node to stake a large amount of cryptocurrency.
   • BBy making it costly to create many fake identities because each identity would need to perform computational work.
   • CBy limiting the number of nodes that can join the network.
   • DBy requiring nodes to pass a CAPTCHA test before joining the network.
   Reveal Solution Discussion Select an answer first
6. 15application · medium

   A developer is tuning a private PoW testnet to mimic Bitcoin's block-time stability. The testnet currently produces blocks every 2 minutes on average, but the team wants a 10-minute average. The developer adjusts the difficulty target. What is the immediate effect of this change on the mining process?

   • AMiners must find a block hash with more leading zero bits, increasing the average search time.
   • BMiners will automatically receive more transactions per block to fill the extra time.
   • CMiners will switch to a less energy-intensive mining algorithm to compensate for the longer search.
   • DMiners must use a different hash algorithm that produces longer outputs.
   Reveal Solution Discussion Select an answer first