Quantum Computing and Blockchain BDC Practice Questions (Page 3)

Questions 11–15

1. 11application · medium

   A research consortium is building a blockchain that uses a hybrid quantum-classical system. They want to use a quantum computer to generate true randomness for a lottery smart contract, but they also need the blockchain to remain fully functional when the quantum computer is offline. What is the best design?

   • AReplace the consensus algorithm with a quantum-based consensus that requires all nodes to have quantum computers.
   • BStore quantum-generated random numbers on-chain and use them for all future blocks, ignoring the need for new randomness.
   • CRequire every block to include a quantum-generated random number, halting the chain if the quantum computer is unavailable.
   • DUse the quantum computer as an oracle that submits random numbers to the smart contract, with a classical fallback that uses a cryptographically secure pseudo-random generator.
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2. 12foundation · easy

   Which cryptographic algorithm used in blockchain is most directly threatened by Shor's algorithm on a sufficiently powerful quantum computer?

   • ASHA-256
   • BKeccak-256
   • CRSA
   • DAES-256
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4. 13application · medium

   A blockchain platform wants to protect its users' funds from a 'harvest now, decrypt later' attack, where an adversary collects encrypted data today and decrypts it once a quantum computer is available. Which strategy is most effective?

   • ARely on the assumption that quantum computers will not be powerful enough for several decades.
   • BIncrease the key length of all current cryptographic algorithms to the maximum supported size.
   • CUse a longer hash function for all data stored on the blockchain.
   • DMigrate to post-quantum cryptographic algorithms for all encryption and signing operations immediately.
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5. 14application · medium

   A blockchain company is experimenting with a hybrid quantum-classical system to improve the efficiency of zero-knowledge proofs (ZKPs). They have access to a quantum annealer. Which task is most suitable for the quantum annealer?

   • AVerifying the ZKP proof.
   • BOptimizing the polynomial constraints in a zk-SNARK circuit.
   • CGenerating the random challenge in the ZKP protocol.
   • DPerforming the elliptic curve scalar multiplication in the ZKP.
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6. 15foundation · easy

   Which statement correctly describes a qubit in quantum computing?

   • AA qubit is a unit of quantum entanglement that has no relation to binary states.
   • BA qubit can only be 0 or 1, but it can be copied easily.
   • CA qubit can represent both 0 and 1 simultaneously due to superposition.
   • DA qubit is a classical bit that can be either 0 or 1 at any time.
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