Symmetric Cryptography and Key Algorithms BDC Practice Questions (Page 4)

Questions 16–20

1. 16application · medium

   A company has been using the same symmetric key for the past five years to encrypt all data in its application. The security team has decided to implement key rotation. What is the primary reason for rotating the key?

   • ATo improve the performance of the encryption algorithm by using a fresh key.
   • BTo reduce the risk of key compromise by limiting the amount of data encrypted with a single key.
   • CTo ensure that the key is compatible with the latest version of the encryption software.
   • DTo allow the company to use a different encryption algorithm in the future.
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2. 17application · medium

   A startup is building a peer-to-peer file-sharing system where users encrypt files before uploading. They need to ensure that only the intended recipient can decrypt the file. What is the most practical approach?

   • ASend the symmetric key in a separate message without encryption
   • BUse only asymmetric encryption for the file
   • CEncrypt the file with a symmetric key and encrypt that key with the recipient's public key
   • DUse a single shared symmetric key for all users
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4. 18application · medium

   A legacy system uses DES to encrypt data at rest. The security team wants to upgrade to a modern algorithm while maintaining compatibility with existing data. What is the best approach?

   • AContinue using DES because it is still functional
   • BUse AES for new data and leave old data as is
   • CDecrypt all data with the old key and re-encrypt with AES
   • DSwitch to 3DES with the same key
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5. 19application · medium

   A blockchain startup needs to encrypt a large dataset of transaction metadata before storing it in a distributed file system. The data is static, and the team wants to minimize the risk of pattern leakage while keeping encryption fast. Which mode of operation should they choose?

   • AAES-GCM
   • BAES-CBC
   • CAES-ECB
   • DAES-CTR
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6. 20application · medium

   A legacy system in a hospital still uses DES to encrypt patient records. The security team has been asked to migrate to a more secure algorithm. The system's hardware is old and does not support AES-NI instructions. The team needs a symmetric algorithm that is widely supported and provides better security than DES. Which algorithm should they choose?

   • A3DES with three independent keys, because it is a drop-in replacement for DES and is still considered secure.
   • BChaCha20, because it is a stream cipher that is fast in software and provides strong security.
   • CBlowfish, because it is a fast block cipher that is a direct replacement for DES.
   • DAES-256, because it is the industry standard and provides the highest level of security.
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