Quantum Computing and Blockchain BDC Practice Questions (Page 2)

Questions 6–10

1. 6expert · hard

   A blockchain startup is building a hybrid quantum-classical system where a quantum computer is used to generate randomness for a lottery smart contract. The quantum computer is accessed via a cloud service and has a high latency. The smart contract needs to produce a random number within a 10-second window. What is the best design?

   • AUse a classical random number generator and ignore the quantum computer.
   • BUse a pre-generated list of quantum random numbers stored on-chain.
   • CRequire the smart contract to wait for the quantum computer's response every time.
   • DUse a classical pseudo-random generator as the primary source and use the quantum computer to periodically reseed it.
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2. 7application · medium

   A blockchain platform is exploring the use of quantum computing to improve smart contract execution. They have a hybrid quantum-classical system where a quantum processor can be used as a coprocessor. Which use case is most realistic for near-term quantum advantage?

   • AReplacing the blockchain's consensus algorithm with a quantum algorithm.
   • BStoring smart contract state in quantum memory.
   • COptimizing complex combinatorial problems, such as supply chain logistics, that are part of a smart contract.
   • DExecuting all smart contract logic on the quantum processor.
   Reveal Solution Discussion Select an answer first
4. 8application · medium

   A consortium blockchain network is planning a migration to post-quantum cryptography. The network currently uses RSA for transaction signing and ECDH for key exchange between nodes. The team wants to minimize the performance impact on transaction throughput while ensuring long-term security. Which approach best meets these requirements?

   • AAdopt a lattice-based signature scheme like CRYSTALS-Dilithium for signing and a lattice-based KEM like CRYSTALS-Kyber for key exchange.
   • BUse symmetric encryption with AES-256 for all communications and signatures.
   • CContinue using RSA but increase the key size to 8192 bits.
   • DReplace RSA with ECDSA and use a larger curve like P-521.
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5. 9expert · hard

   A consortium blockchain is designing a quantum-resistant upgrade. They have a large existing user base and want to minimize disruption. They also want to ensure that funds are not lost if a user's quantum-resistant key is compromised. Which design is most robust?

   • AUse a post-quantum signature scheme but do not allow key rotation.
   • BUse a hybrid signature scheme that requires both a classical and a post-quantum signature for every transaction, and implement a recovery mechanism that allows users to rotate keys with a delay.
   • CUse only a post-quantum signature scheme and rely on the user to keep their key safe.
   • DUse a classical signature scheme with a longer key and hope that quantum computers are not developed soon.
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6. 10foundation · easy

   What is the role of entanglement in quantum computing?

   • AIt ensures that qubits remain stable and do not decohere during computation.
   • BIt enables qubits to store more than one bit of information by using multiple energy levels.
   • CIt allows quantum computers to run multiple programs at the same time on the same hardware.
   • DIt allows qubits to be correlated so that the state of one instantly influences the state of another, even when separated.
   Reveal Solution Discussion Select an answer first