Advanced Cryptographic Mechanisms in Blockchain Security BBLC Practice Questions (Page 5)

Questions 21–25

1. 21foundation · easy

   Which of the following is an example of a post-quantum cryptographic approach being considered for blockchain?

   • AUsing symmetric encryption for digital signatures
   • BLattice-based cryptography
   • CUsing MD5 for hashing
   • DIncreasing RSA key sizes to 8192 bits
   Reveal Solution Discussion Select an answer first
2. 22expert · hard

   A supply-chain blockchain needs to prove to customs authorities that a shipment's declared value is below a threshold without revealing the exact value. The proof must be verifiable by the authorities without interacting with the shipper. Which technique should be used?

   • AHash of the value, with the authority comparing to a public list.
   • BDigital signature over the value, with the value encrypted.
   • CHomomorphic encryption of the value, with the authority decrypting it.
   • DZero-knowledge proof that the value is below the threshold, generated by the shipper.
   Reveal Solution Discussion Select an answer first
4. 23foundation · easy

   What is the primary advantage of using a Merkle tree to store transaction hashes in a block?

   • AIt reduces the block size by removing duplicate transactions
   • BIt provides a private key for each transaction in the block
   • CIt allows a node to verify a single transaction without downloading the entire block
   • DIt encrypts the transactions so that only the block producer can read them
   Reveal Solution Discussion Select an answer first
5. 24expert · hard

   A blockchain voting system must allow voters to prove they are eligible without revealing their identity or vote. The system also needs to prevent double voting. Which cryptographic mechanism best satisfies both privacy and uniqueness?

   • AHomomorphic encryption of the vote.
   • BHashing the voter ID and vote together.
   • CDigital signatures with the voter's private key.
   • DZero-knowledge proofs combined with a nullifier that is unique per voter.
   Reveal Solution Discussion Select an answer first
6. 25expert · hard

   A blockchain network is planning for quantum resistance. They must choose a post-quantum signature scheme. The network has limited bandwidth and requires fast verification. Which type of post-quantum algorithm is most appropriate?

   • ACode-based signatures, which have large signatures.
   • BLattice-based signatures (e.g., Dilithium), which offer a balance of key size, signature size, and speed.
   • CMultivariate-based signatures, which have large public keys.
   • DHash-based signatures (e.g., SPHINCS+), which have small signatures but require state management.
   Reveal Solution Discussion Select an answer first