Cryptographic Principles and Their Role in Blockchain BBLC Practice Questions (Page 2)

Questions 6–10

1. 6application · medium

   A privacy-focused blockchain wants to allow users to prove that they have sufficient funds for a transaction without revealing their total balance or the specific inputs being spent. Which cryptographic technique enables this?

   • AUse a digital signature from the sender to prove they own the inputs, and rely on the blockchain's public ledger to show the balance.
   • BEncrypt the transaction inputs with the recipient's public key so only the recipient can see the amounts.
   • CHash the transaction inputs and include the hash in the block; the network verifies the hash matches the sender's stored hash.
   • DUse a zero-knowledge proof to demonstrate that the sum of hidden inputs is greater than or equal to the transaction amount, without revealing the inputs.
   Reveal Solution Discussion Select an answer first
2. 7application · medium

   A privacy-focused blockchain allows users to prove they hold a valid digital asset without revealing which asset or its history. Which cryptographic technique enables this?

   • AA digital signature over the asset's hash
   • BA public-key encryption of the asset's details
   • CA zero-knowledge proof that demonstrates possession of a valid asset
   • DA Merkle proof that the asset is in the blockchain
   Reveal Solution Discussion Select an answer first
4. 8expert · hard

   A user's hardware wallet was lost, but they have a 24-word seed phrase stored in a fireproof safe. They want to restore their funds on a new wallet. What is the correct process?

   • AUse the seed phrase to sign transactions directly without a wallet
   • BContact the hardware wallet manufacturer to recover the private keys from the lost device
   • CEnter the seed phrase into a new hardware wallet to regenerate the private keys
   • DUse the seed phrase to create a new set of private keys on a software wallet
   Reveal Solution Discussion Select an answer first
5. 9foundation · easy

   What is the core idea of a zero-knowledge proof?

   • ATo create a digital signature that hides the signer's identity
   • BTo encrypt data so that only the receiver can decrypt it
   • CTo prove knowledge of a secret without revealing the secret itself
   • DTo compress transaction data to save space
   Reveal Solution Discussion Select an answer first
6. 10expert · hard

   A proof-of-work blockchain is experiencing faster block times than expected because miners have deployed more efficient hardware. The network's difficulty adjustment algorithm is designed to maintain a 10-minute average block time. Which action should the network take to restore the target block time?

   • ADecrease the difficulty target (make the target a smaller number) so that the required hash must have more leading zeros, increasing the average time to find a block.
   • BIncrease the nonce range to allow miners to try more values per second.
   • CIncrease the difficulty target (make the target a larger number) so that more hashes are required to find a block.
   • DChange the hash function to a slower algorithm to reduce the hash rate.
   Reveal Solution Discussion Select an answer first