Lattice-Based and Post-Quantum Cryptography ECES Practice Questions (Page 5)

Questions 21–25

1. 21application · medium

   A software company is integrating a post-quantum digital signature scheme into its firmware update process. The firmware is deployed on resource-constrained IoT devices with limited memory and CPU. The team needs a signature scheme with small signatures and fast verification. Which NIST-selected algorithm is the most appropriate choice?

   • ASPHINCS+, because it is hash-based and has very small public keys, making it easy to store on devices.
   • BDilithium, because it offers a good balance of performance and key/signature sizes, and is designed for general-purpose use.
   • CFalcon, because it provides the smallest signature sizes among the NIST-selected signature schemes, which is critical for constrained devices.
   • DKyber, because it is a lattice-based KEM that can also be used for signatures with minor modifications.
   Reveal Solution Discussion Select an answer first
2. 22application · medium

   A cryptography team is researching multivariate polynomial cryptography for a new digital signature scheme. They are considering the Rainbow signature scheme. Which statement correctly describes a challenge of multivariate schemes like Rainbow?

   • AThey have very small signatures, but the signing process is extremely slow.
   • BThey require a trusted setup to generate the public parameters.
   • CThey are based on the difficulty of solving systems of linear equations, which is easy for quantum computers.
   • DThey have very large public keys, often hundreds of kilobytes, which limits their use in constrained environments.
   Reveal Solution Discussion Select an answer first
4. 23application · medium

   A cryptographic team is reviewing post-quantum families and notes that one family offers very small key sizes and fast operations but was not selected by NIST due to performance issues and security concerns. Which family is this?

   • ALattice-based cryptography
   • BHash-based cryptography
   • CCode-based cryptography
   • DIsogeny-based cryptography
   Reveal Solution Discussion Select an answer first
5. 24expert · hard

   A software company is developing a secure boot mechanism for embedded devices. They need a digital signature scheme that can be verified very quickly, even on low-power processors. They are considering Dilithium and Falcon. Which scheme should they choose, and why?

   • ADilithium, because it has faster verification than Falcon on most platforms.
   • BFalcon, because it has smaller signatures, which reduces the amount of data to verify.
   • CEither scheme, because both have identical verification speeds.
   • DSPHINCS+, because it is hash-based and has very fast verification.
   Reveal Solution Discussion Select an answer first
6. 25expert · hard

   A large enterprise is planning its migration to post-quantum cryptography. The enterprise has a mix of legacy systems that cannot be upgraded quickly and new systems that can support post-quantum algorithms. The security team is concerned about 'harvest now, decrypt later' attacks. Which migration strategy best addresses this concern while maintaining compatibility?

   • AUse only hash-based signatures for all communications
   • BImmediately replace all classical algorithms with post-quantum algorithms on every system
   • CDeploy hybrid schemes on all systems that support them, and use classical-only for legacy systems
   • DWait until quantum computers are commercially available before making any changes
   Reveal Solution Discussion Select an answer first