Quantum Computing and Blockchain BDC Practice Questions (Page 8)

Questions 36–40

1. 36application · medium

   A blockchain architect is preparing a roadmap for a public blockchain. They want to ensure that the network can transition to quantum-resistant cryptography without requiring users to migrate to new addresses. Which approach is most practical?

   • AKeep the current address format and simply increase the hash length of the address.
   • BDesign a signature scheme that allows the public key to be derived from the address only at the time of spending, using a quantum-resistant algorithm.
   • CRequire all users to generate new quantum-resistant addresses and transfer their funds.
   • DUse a sidechain for quantum-resistant transactions and keep the main chain unchanged.
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2. 37application · medium

   A government agency is building a blockchain-based voting system. They require that all communication between nodes be secure against quantum attacks, and they have the budget to install specialized hardware. They also need to ensure that any attempt to intercept communications is immediately detectable. Which technology should they use?

   • APost-quantum key encapsulation mechanisms (KEMs) over the internet.
   • BClassical TLS with a 4096-bit RSA certificate.
   • CQuantum entanglement-based direct communication without any classical encryption.
   • DQuantum Key Distribution (QKD) for key exchange, combined with classical symmetric encryption for data.
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4. 38expert · hard

   A blockchain developer is designing a post-quantum upgrade for a network that currently uses ECDSA. They want to ensure that the upgrade is secure against both quantum and classical attacks. Which approach is most appropriate?

   • AUse a hybrid signature that combines ECDSA with a post-quantum signature, so that the security is the intersection of both.
   • BReplace ECDSA with a post-quantum signature and remove all classical algorithms.
   • CUse a longer ECDSA key and a longer hash function.
   • DKeep ECDSA and add a post-quantum key encapsulation mechanism for key exchange.
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5. 39foundation · easy

   Which of the following is a typical use case for a hybrid quantum-classical approach in blockchain?

   • AReplacing all classical nodes with quantum computers to run the entire blockchain.
   • BUsing a quantum computer to solve complex optimization problems for consensus or routing while classical nodes handle standard transactions.
   • CUsing quantum entanglement to instantly sync all blockchain nodes.
   • DUsing quantum computers to mine all blocks and eliminate the need for consensus.
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6. 40foundation · easy

   How can quantum key distribution (QKD) be used to secure blockchain communications?

   • ABy securely distributing symmetric keys that can be used to encrypt communication between blockchain nodes.
   • BBy using quantum computers to mine blocks faster.
   • CBy replacing the blockchain's consensus algorithm with a quantum-based one.
   • DBy storing the entire blockchain on quantum memory.
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