Asymmetric Cryptography and Key Algorithms BDC Practice Questions (Page 3)

Questions 11–15

1. 11expert · hard

   A security auditor is reviewing a blockchain system where transactions are signed with ECDSA. The auditor wants to ensure that a signature cannot be replayed in a different context. What additional mechanism is typically used?

   • AEncrypt the signature with the recipient's public key.
   • BHash the signature twice.
   • CInclude a unique nonce or transaction ID in the signed data.
   • DUse a longer private key.
   Reveal Solution Discussion Select an answer first
2. 12application · medium

   A developer is generating a key pair for a blockchain wallet. Which practice is essential for the security of the wallet?

   • AGenerate the key pair using a weak random number generator.
   • BStore the private key in a hardware security module (HSM) or secure enclave.
   • CShare the private key with a trusted third party for backup.
   • DUse the same private key for multiple wallets.
   Reveal Solution Discussion Select an answer first
4. 13expert · hard

   A developer is implementing a multi-signature wallet that requires two out of three authorized users to sign a transaction. What is the primary security benefit of this design?

   • AIt reduces the risk of a single compromised private key being sufficient to authorize a transaction.
   • BIt makes the wallet address shorter and easier to share.
   • CIt allows the wallet to recover lost private keys automatically.
   • DIt encrypts the transaction data so only the signers can read it.
   Reveal Solution Discussion Select an answer first
5. 14expert · hard

   A blockchain developer is designing a wallet that supports hierarchical deterministic (HD) key generation. The wallet derives a master key from a seed phrase, and then derives child keys for each address. The developer needs to ensure that if a child private key is compromised, the master key and other child keys remain secure. Which property of HD wallets provides this?

   • AChild keys are derived using a one-way hash function from the master key, so a child key cannot be used to reverse-engineer the master key.
   • BThe master key is encrypted with the child key, so it cannot be recovered without the child key.
   • CChild keys are generated independently from the master key using random numbers.
   • DChild keys are stored on separate hardware devices, so compromising one does not affect the others.
   Reveal Solution Discussion Select an answer first
6. 15foundation · easy

   What is the recommended practice for storing a private key used in asymmetric cryptography?

   • AEncrypt it with a strong passphrase and store it in a secure hardware module or a trusted key store.
   • BShare it with a trusted third party for backup purposes.
   • CStore it in a plain text file on the local disk for easy access.
   • DEmbed it in the application source code for convenience.
   Reveal Solution Discussion Select an answer first