Symmetric Cryptography and Key Algorithms BDC Practice Questions (Page 5)

Questions 21–25

1. 21expert · hard

   A startup is building a peer-to-peer file-sharing application where users directly exchange encrypted files. They want to use symmetric encryption for speed. What is the biggest challenge they will face, and what is the best solution?

   • AThe challenge is the lack of authentication; the solution is to use a digital signature with a public key infrastructure.
   • BThe challenge is the speed of symmetric encryption; the solution is to use a faster algorithm like ChaCha20.
   • CThe challenge is key distribution; the solution is to use a Diffie-Hellman key exchange to establish a shared symmetric key.
   • DThe challenge is the scalability of symmetric encryption; the solution is to use a central server to manage keys.
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2. 22expert · hard

   A company is evaluating whether to use symmetric or asymmetric encryption for a new system that will encrypt data at rest. The data is stored on a central server and accessed by multiple clients. Which statement accurately reflects a key trade-off?

   • ASymmetric encryption does not require key management because the key is embedded in the hardware.
   • BAsymmetric encryption is faster than symmetric encryption for large data sets.
   • CAsymmetric encryption is easier to implement because it does not require key distribution.
   • DSymmetric encryption is faster but requires a secure method to distribute the key to all clients.
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4. 23foundation · easy

   Which of the following is a recommended practice for securely storing symmetric keys?

   • AUse a hardware security module (HSM) or a secure key vault.
   • BStore keys in plaintext within the application source code.
   • CEncrypt the key with the same key (self-encryption).
   • DStore keys in a shared network folder with read-only permissions.
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5. 24application · medium

   A small company uses a symmetric key to encrypt backups. The key is stored on a USB drive in a safe. An employee accidentally emails the key to a vendor. What is the most appropriate immediate action?

   • ARotate the key and re-encrypt all backups with the new key
   • BChange the encryption algorithm but keep the same key
   • CAsk the vendor to delete the email and keep using the key
   • DContinue using the key because the vendor is trusted
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6. 25application · medium

   A developer is encrypting a large file that will be stored in the cloud. They need to be able to decrypt a specific portion of the file without decrypting the entire file. Which mode of operation supports random access decryption?

   • ACTR mode
   • BGCM mode
   • CECB mode
   • DCBC mode
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