Cryptographic Techniques and Algorithms NDE Practice Questions (Page 4)

Questions 16–20

1. 16expert · hard

   A government agency requires that all outgoing documents be signed with a digital signature that can be verified for at least 20 years. They are concerned about the long-term security of the signature algorithm. Which approach should they take?

   • AUse MD5 for the hash and RSA-1024 for the signature to ensure compatibility with older systems.
   • BUse a strong hash function like SHA-256 and a digital signature algorithm with a sufficiently large key, and plan to re-sign documents before the algorithm becomes weak.
   • CUse a symmetric key to sign the documents and keep the key secret for 20 years.
   • DUse a hash of the document as the signature and store the hash in a public database.
   Reveal Solution Discussion Select an answer first
2. 17application · medium

   A small company needs to encrypt files stored on a shared network drive so that only employees with the correct password can read them. They want the encryption to be fast enough for large files and do not want to manage individual public/private key pairs for each employee. Which approach best meets these requirements?

   • AUse Diffie-Hellman to establish a separate key for each file and store the keys in a public folder.
   • BUse SHA-256 to encrypt the files and share the hash as the decryption key.
   • CUse RSA to encrypt each file with the manager's public key and store the private key on the server.
   • DUse AES with a shared passphrase-derived key, and distribute the passphrase only to authorized employees.
   Reveal Solution Discussion Select an answer first
4. 18foundation · easy

   Which countermeasure is most effective against a brute force attack on an encryption key?

   • AUsing a hash function
   • BUsing a shorter key length
   • CUsing a public key for encryption
   • DUsing a longer key length
   Reveal Solution Discussion Select an answer first
5. 19application · medium

   A security team wants to store user passwords in a database in a way that resists brute-force and rainbow-table attacks. Which method should they use?

   • AStore the passwords encrypted with AES using a hard-coded key in the application.
   • BStore a salted hash of each password using a slow, keyed hash function like bcrypt or Argon2.
   • CStore only the MD5 hash of each password without a salt.
   • DStore the passwords in plaintext but restrict database access to administrators only.
   Reveal Solution Discussion Select an answer first
6. 20application · medium

   A company wants to allow external partners to send encrypted messages to the company's support department without requiring the partners to install any special software. The support department needs to decrypt the messages. Which setup should the company implement?

   • AUse a hash of the message as the encryption key and send the hash separately.
   • BAsk partners to encrypt messages with the support department's private key.
   • CShare a symmetric key with each partner over email before they send messages.
   • DPublish the support department's public key on the company website; partners encrypt messages with that key.
   Reveal Solution Discussion Select an answer first