Asymmetric Encryption and Defensive Coding CASENET Practice Questions (Page 6)

Questions 26–28

1. 26expert · hard

   A .NET developer is implementing RSA encryption for a legacy system that only supports PKCS#1 v1.5 padding. The system is exposed to the internet and handles sensitive data. Which mitigation is most effective to reduce the risk of padding oracle attacks?

   • AReturn a generic error message for any decryption failure.
   • BUse a longer RSA key (e.g., 4096 bits) with PKCS#1 v1.5.
   • CUpgrade the system to support OAEP padding.
   • DUse a random symmetric key to encrypt the data and encrypt that key with RSA.
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2. 27application · medium

   A developer is implementing RSA encryption in a .NET application and needs to choose a padding scheme. The application will encrypt small session keys that are sent to a server. Which padding scheme should the developer use to prevent padding-oracle attacks?

   • APKCS#7 padding
   • BPKCS#1 v1.5 padding
   • COAEP padding with SHA-256
   • DNo padding
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3. 28expert · hard

   A .NET developer is designing a system that encrypts large files for multiple recipients. Each recipient should be able to decrypt the file independently. Which approach is most efficient and secure?

   • AEncrypt the file with a single symmetric key and share that key with all recipients.
   • BEncrypt the file with the sender's private key and send it to all recipients.
   • CEncrypt the file once with a random symmetric key, then encrypt that key separately with each recipient's public key.
   • DEncrypt the file separately with each recipient's public key.
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