Quantum Computing and Blockchain BDC Practice Questions (Page 5)

Questions 21–25

1. 21application · medium

   A bank is deploying a blockchain-based inter-bank settlement system. They want to ensure that the communication channel between two data centers is protected against future quantum eavesdropping. They have a dedicated dark fiber link between the sites. Which approach should they choose?

   • AImplement Quantum Key Distribution (QKD) over the dark fiber to generate symmetric keys for encrypting blockchain messages.
   • BUse a longer RSA key for the TLS handshake between the data centers.
   • CUse a post-quantum key encapsulation mechanism (KEM) over the existing internet connection.
   • DRely on the blockchain's consensus mechanism to detect any tampering with messages.
   Reveal Solution Discussion Select an answer first
2. 22foundation · easy

   Which design strategy is commonly proposed to make a blockchain quantum-resistant?

   • AUsing a proof-of-stake consensus to reduce energy consumption.
   • BReplacing ECDSA with a post-quantum signature scheme like hash-based signatures.
   • CStoring all private keys on hardware wallets.
   • DIncreasing the block size to accommodate more transactions.
   Reveal Solution Discussion Select an answer first
4. 23application · medium

   A blockchain startup is evaluating the long-term security of its existing public blockchain network. The team is concerned that a future large-scale quantum computer could recover the private keys of users from their public keys. The network currently uses ECDSA for digital signatures and SHA-256 for hashing. Which immediate design change would most directly mitigate the identified threat?

   • AReplace ECDSA with a hash-based signature scheme such as XMSS.
   • BUse a longer nonce in the ECDSA signing process.
   • CIncrease the ECDSA key size from 256 to 512 bits.
   • DSwitch the hashing algorithm from SHA-256 to SHA-3.
   Reveal Solution Discussion Select an answer first
5. 24foundation · easy

   What is the fundamental security property provided by quantum key distribution (QKD)?

   • AIt detects any eavesdropping attempt on the key exchange due to the disturbance of quantum states.
   • BIt uses quantum entanglement to teleport data instantly.
   • CIt encrypts data using quantum computers, making it unbreakable.
   • DIt allows two parties to communicate without any physical channel.
   Reveal Solution Discussion Select an answer first
6. 25expert · hard

   A blockchain think tank is analyzing the future impact of quantum computing on blockchain. They have identified that quantum computers could break current digital signatures, but also could enable new types of smart contracts. They are considering a roadmap for the next decade. Which strategy is most prudent?

   • AFocus solely on developing quantum-enhanced smart contracts, as they are the future.
   • BWait for quantum computers to become mainstream before making any decisions.
   • CAbandon blockchain technology because it will be obsolete.
   • DInvest in post-quantum cryptography research and develop a migration plan, while exploring quantum-enhanced smart contracts.
   Reveal Solution Discussion Select an answer first