Cryptographic Principles and Their Role in Blockchain BBLC Practice Questions (Page 5)

Questions 21–25

1. 21foundation · easy

   What is the primary purpose of a Merkle tree in a blockchain?

   • ATo efficiently verify the integrity and consistency of a large set of data
   • BTo encrypt transaction data before it is added to a block
   • CTo generate public and private key pairs for users
   • DTo store the actual transaction data in a compressed format
   Reveal Solution Discussion Select an answer first
2. 22foundation · easy

   In blockchain, what is the primary role of cryptographic hash functions?

   • AProviding a mechanism for user authentication through passwords
   • BGenerating private keys from public keys
   • CEncrypting transaction data so only authorized parties can read it
   • DEnsuring data integrity by creating a unique, fixed-size fingerprint of data
   Reveal Solution Discussion Select an answer first
4. 23expert · hard

   A blockchain network currently uses ECDSA (Elliptic Curve Digital Signature Algorithm) for transaction signatures. A security researcher warns that a sufficiently powerful quantum computer could forge signatures by deriving private keys from public keys. The network wants to protect against this threat while maintaining compatibility with existing wallets. Which strategy is the most practical?

   • ASwitch to a proof-of-stake consensus to eliminate the need for digital signatures.
   • BImplement a hybrid signature scheme that combines ECDSA with a post-quantum signature (e.g., hash-based or lattice-based) and require both for transactions.
   • CReplace ECDSA with RSA signatures, which are believed to be quantum-resistant.
   • DIncrease the ECDSA key size to 512 bits to make it quantum-resistant.
   Reveal Solution Discussion Select an answer first
5. 24expert · hard

   A proof-of-work blockchain is experiencing a security issue: a mining pool has accumulated more than 51% of the network's hash rate. The network's governance wants to reduce the risk of a 51% attack. Which option is most directly effective?

   • AImplement a checkpointing mechanism that finalizes blocks and prevents deep reorganizations
   • BReduce the block time to make attacks harder
   • CChange the proof-of-work algorithm to one that is ASIC-resistant
   • DIncrease the block reward to attract more miners
   Reveal Solution Discussion Select an answer first
6. 25application · medium

   A blockchain-based voting system records each vote as a transaction. An auditor wants to verify that a particular voter's ballot was included in a block without revealing how that voter voted. What is the most efficient way to provide this assurance?

   • AProvide a Merkle proof that the ballot hash is included in the block's Merkle root
   • BProvide the auditor with the voter's private key to sign a verification request
   • CProvide the auditor with the full list of transactions in the block
   • DProvide a digital signature from the election authority over the entire block
   Reveal Solution Discussion Select an answer first