Common Threats and Blockchain Security Best Practices BBLC Practice Questions (Page 3)

Questions 11–15

1. 11expert · hard

   A blockchain network is considering a change to its consensus mechanism to improve security. The network currently uses proof-of-work (PoW) and has a hash rate that is relatively low, making it vulnerable to a 51% attack. The team is evaluating two options: (1) switch to proof-of-stake (PoS) with a large validator set, or (2) keep PoW but increase the block reward to attract more miners. Which option is the MORE effective long-term solution to reduce the risk of a 51% attack?

   • ASwitch to a delegated proof-of-stake (DPoS) with a small validator set.
   • BSwitch to PoS with a large validator set and slashing.
   • CKeep PoW and increase the block reward to attract more miners.
   • DKeep PoW but reduce the block time to make it harder to reorg.
   Reveal Solution Discussion Select an answer first
2. 12foundation · easy

   Which cryptographic mechanism is used to prove that a transaction was authorized by the holder of a specific private key?

   • ASymmetric encryption
   • BHash function
   • CDigital signature
   • DMerkle tree
   Reveal Solution Discussion Select an answer first
4. 13application · medium

   A smart contract for a decentralized exchange has a function that allows users to withdraw funds. The contract does not check the return value of an external call. Which vulnerability is this most likely to introduce?

   • AReentrancy attack
   • BPhishing attack
   • CUnchecked external call vulnerability
   • DInteger overflow
   Reveal Solution Discussion Select an answer first
5. 14application · medium

   A cryptocurrency exchange is implementing a new withdrawal system. To prevent unauthorized withdrawals even if a user's password is compromised, the exchange wants to require a second factor that is cryptographically tied to the user's device. Which approach best meets this requirement?

   • AAsk the user to answer a set of personal security questions before withdrawal.
   • BRequire the user to enter a code from an authenticator app that is synchronized with the server.
   • CSend a one-time passcode (OTP) via SMS to the user's registered phone number.
   • DUse a hardware security key that generates a digital signature for each authentication request.
   Reveal Solution Discussion Select an answer first
6. 15foundation · easy

   What is the primary purpose of economic incentives in a proof-of-stake consensus mechanism?

   • ATo ensure that all validators have equal voting power.
   • BTo align the interests of validators with the security and integrity of the network.
   • CTo allow validators to create unlimited blocks.
   • DTo eliminate the need for cryptographic hashing.
   Reveal Solution Discussion Select an answer first