Cryptographic Principles BDC Practice Questions (Page 4)

Questions 16–20

1. 16expert · hard

   A blockchain network uses a digital signature scheme. An attacker has discovered that the random number generator used to create private keys is flawed, producing a limited set of possible keys. Which attack is the attacker most likely to execute?

   • ASide-channel attack
   • BBrute-force attack
   • CReplay attack
   • DMan-in-the-middle attack
   Reveal Solution Discussion Select an answer first
2. 17foundation · easy

   In a blockchain system, which cryptographic approach is commonly used to allow anyone to verify a transaction's authenticity without sharing a secret?

   • AHash-based message authentication code (HMAC)
   • BSymmetric cryptography
   • CAsymmetric cryptography
   • DSteganography
   Reveal Solution Discussion Select an answer first
4. 18foundation · easy

   Which cryptographic principle is primarily concerned with proving that a specific party performed a particular action?

   • AIntegrity
   • BConfidentiality
   • CAvailability
   • DNon-repudiation
   Reveal Solution Discussion Select an answer first
5. 19application · medium

   An organization uses a hardware security module (HSM) to store the private keys used for code signing. The security team wants to rotate the signing key annually without invalidating previously signed artifacts. What is the best practice?

   • AReuse the same key pair but change the certificate's expiration date.
   • BDelete the old private key immediately after generating the new key pair.
   • CEncrypt the old private key with the new public key and store it in the HSM.
   • DGenerate a new key pair and keep the old key available for verification until all signed artifacts expire.
   Reveal Solution Discussion Select an answer first
6. 20application · medium

   A security team notices that an attacker is submitting a large number of transactions to a blockchain network, each with a different nonce, in an attempt to guess a valid signature. Which attack is this, and what is the most effective mitigation?

   • ABrute-force attack; use a larger key size or a signature algorithm with sufficient security margin.
   • BSide-channel attack; use constant-time signing.
   • CMan-in-the-middle attack; use a secure channel.
   • DReplay attack; add a timestamp to each transaction.
   Reveal Solution Discussion Select an answer first