Symmetric Cryptography and Key Algorithms BDC Practice Questions (Page 7)

Questions 31–35

1. 31application · medium

   A developer is building a mobile messaging app that needs to encrypt messages on low-power devices. The app must provide authenticated encryption and be resistant to side-channel attacks. Which algorithm is most appropriate?

   • A3DES
   • BChaCha20-Poly1305
   • CAES-ECB
   • DDES
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2. 32expert · hard

   A company uses a symmetric key to encrypt data in a multi-tenant cloud database. The company wants to ensure that each tenant's data is encrypted with a different key, and that keys are rotated without downtime. What is the best approach?

   • AUse the same key but change the IV for each tenant
   • BStore all tenant keys in a plaintext configuration file
   • CUse a single master key for all tenants
   • DGenerate a unique data encryption key (DEK) per tenant and encrypt each DEK with a master key
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4. 33application · medium

   A developer is implementing encryption for a network protocol that sends small, fixed-size messages. The messages are highly structured and contain many repeated fields. Which mode of operation should be avoided to prevent information leakage?

   • ACBC mode with a random IV.
   • BGCM mode with a unique IV.
   • CCTR mode with a unique nonce.
   • DECB mode.
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5. 34application · medium

   A small company is setting up encryption for its internal file server. They plan to use a symmetric key to encrypt files. The key will be shared among a small team of administrators. What is the most important consideration for key distribution?

   • AUsing a key distribution center (KDC) to automatically distribute the key.
   • BSending the key via email to all administrators for convenience.
   • CPosting the key on a shared internal wiki page that only administrators can access.
   • DUsing a secure out-of-band channel, such as a physical meeting or a trusted courier, to share the key.
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6. 35expert · hard

   A security team is implementing a key management system for a multi-tenant SaaS application. Each tenant's data is encrypted with a unique symmetric key. The system must allow the support team to access a tenant's data for troubleshooting, but only with explicit approval from the tenant. What is the best approach?

   • AGive the support team the master key and rely on them to be careful.
   • BUse a key management service (KMS) with per-tenant keys and implement an approval workflow for key access.
   • CEncrypt all tenant data with the same key to simplify key management.
   • DStore all tenant keys in a single database and grant the support team access to the database.
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