Advanced Cryptographic Mechanisms in Blockchain Security BBLC Practice Questions (Page 10)

Questions 46–50

1. 46expert · hard

   A blockchain consortium is choosing between ECC (secp256k1) and RSA-2048 for their new ledger. They prioritize transaction throughput and low bandwidth usage, but also want to plan for future quantum threats. Which approach best balances these concerns?

   • AUse ECC now and ignore quantum threats because they are decades away.
   • BUse ECC now for efficiency, but design the protocol to support algorithm agility for future post-quantum migration.
   • CUse a post-quantum algorithm immediately, even though it is less efficient and less standardized.
   • DUse RSA-2048 now because it is more resistant to quantum attacks.
   Reveal Solution Discussion Select an answer first
2. 47application · easy

   A user wants to send a signed transaction on a blockchain. Which key does the user need to keep secret, and which key is shared publicly?

   • AKeep the private key secret; share the public key.
   • BKeep both keys secret.
   • CShare both keys publicly.
   • DKeep the public key secret; share the private key.
   Reveal Solution Discussion Select an answer first
4. 48foundation · easy

   In a blockchain, each block contains the hash of the previous block's header. What is the primary purpose of this design?

   • ATo compress the block data so that blocks take up less storage space
   • BTo provide a private key for signing transactions in the block
   • CTo encrypt the transactions stored in each block
   • DTo create a tamper-evident chain where altering any block changes all subsequent hashes
   Reveal Solution Discussion Select an answer first
5. 49application · medium

   A company is designing a private blockchain for supply chain tracking. They need to ensure that each participant can prove they authorized a transaction, and that the authorization cannot be repudiated. Which combination of cryptographic mechanisms should they use?

   • AEach participant uses a symmetric key shared with the network to encrypt transaction data, and the network logs the encryption timestamp.
   • BEach participant encrypts the transaction with the network's public key, and the network decrypts it with its private key.
   • CEach participant generates an ECC key pair and signs transactions with their private key; the public key is used to verify the signature.
   • DEach participant uses a hash of their identity as a signature, and the network stores the hash in the block.
   Reveal Solution Discussion Select an answer first
6. 50expert · hard

   A financial institution wants to perform risk analysis on encrypted customer data stored on a blockchain. They require that the analysis results be accurate and that the raw data never be exposed to the analytics team. Which approach should they choose?

   • AUse a trusted third party to compute the risk on plaintext data.
   • BDecrypt the data, compute the risk, and re-encrypt the results.
   • CUse zero-knowledge proofs to compute the risk score without revealing the data.
   • DUse homomorphic encryption to compute on encrypted data, with the analytics team only seeing encrypted results.
   Reveal Solution Discussion Select an answer first