Cryptography Concepts EHE Practice Questions (Page 1)

Questions 1–5

1. 1expert · hard

   A company uses a hybrid encryption scheme to secure large files: a random symmetric key encrypts the file, and the symmetric key is encrypted with the recipient's public key. The security team wants to ensure that if a symmetric key is compromised, only the files encrypted with that key are affected. What is the best practice?

   • AUse a unique symmetric key for each file or session.
   • BEncrypt the symmetric key with the sender's private key.
   • CStore the symmetric key in the same location as the encrypted files.
   • DUse the same symmetric key for all files to simplify management.
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2. 2expert · hard

   A company encrypts files with AES-256 and protects the AES key with RSA-2048. The RSA private key is stored on a server that is backed up nightly to an offsite location. The security team wants to ensure that if the offsite backup is stolen, the attacker cannot decrypt the AES key. Which additional control is most effective?

   • AEncrypt the RSA private key with a passphrase derived from a strong password.
   • BRotate the RSA key pair monthly.
   • CStore the RSA private key in a separate file on the same server.
   • DUse a longer RSA key, such as 4096 bits.
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4. 3application · medium

   A company uses symmetric encryption to protect data at rest. An employee who had access to the encryption key leaves the company. The security team wants to ensure that the former employee cannot decrypt data that was encrypted before their departure. What is the most effective action?

   • AKeep the same key but change the encryption algorithm.
   • BRotate the encryption key and re-encrypt all data with the new key.
   • CRevoke the employee's digital certificate.
   • DDelete the employee's user account and change all passwords.
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5. 4foundation · easy

   What is the purpose of key revocation in cryptographic key management?

   • ATo invalidate a compromised or no longer trusted key
   • BTo back up the key to a secure location
   • CTo generate a new key pair for the user
   • DTo encrypt data with a stronger algorithm
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6. 5application · medium

   A company needs to secure file transfers between its headquarters and a branch office. The security team wants to use a cryptographic approach that avoids the need to securely distribute a shared secret beforehand, while still ensuring that only the intended recipient can decrypt the data. Which approach should they implement?

   • AUse the sender's private key to encrypt the file, and the sender's public key to decrypt it.
   • BUse the recipient's public key to encrypt the file, and the recipient's private key to decrypt it.
   • CUse a hash of the file encrypted with the recipient's public key.
   • DUse a single pre-shared key with AES-256 for both encryption and decryption.
   Reveal Solution Discussion Select an answer first