Symmetric Cryptography and Key Algorithms BDC Practice Questions (Page 2)

Questions 6–10

1. 6application · medium

   Two remote offices need to share a symmetric key securely. They have no pre-existing shared secret. Which approach is the most secure way to establish the key?

   • AUse a Diffie-Hellman key exchange over TLS
   • BCall each other and read the key over the phone
   • CSend the key via a courier on a USB drive
   • DEmail the key in a password-protected PDF
   Reveal Solution Discussion Select an answer first
2. 7foundation · easy

   Which symmetric key algorithm is widely considered the modern standard for encrypting data at rest and in transit, and is used by protocols like TLS?

   • ADES
   • B3DES
   • CAES
   • DRC4
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4. 8foundation · easy

   Which statement best describes the core principle of symmetric cryptography?

   • AIt uses a single shared key for both encryption and decryption.
   • BIt uses a public key for encryption and a private key for decryption.
   • CIt uses a key that is derived from the plaintext message itself.
   • DIt uses two different keys: one for encryption and one for decryption.
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5. 9foundation · easy

   In a symmetric encryption system, what is the primary requirement for two parties to communicate securely?

   • AThey must exchange a shared secret key through a secure channel.
   • BThey must use a different key for each message.
   • CThey must have a trusted third party to verify their identities.
   • DThey must use a public key infrastructure to exchange keys.
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6. 10application · medium

   A developer is encrypting a small amount of data (e.g., a session token) and needs to ensure that the same plaintext does not produce the same ciphertext each time. Which mode of operation should they use?

   • AGCM mode with a fixed IV, because it provides authentication and confidentiality.
   • BECB mode, because it is simple and fast.
   • CCBC mode with a random IV, because it ensures that the same plaintext produces different ciphertexts.
   • DCTR mode with a fixed counter, because it is a stream cipher and does not require an IV.
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