Modern Cryptographic Attacks ECES Practice Questions (Page 5)

Questions 21–25

1. 21application · medium

   A security researcher reports that a hardware security module (HSM) leaks information through the time it takes to perform modular exponentiation during RSA private-key operations. You need to select a countermeasure. Which approach is most effective?

   • AAdd random delays before each RSA operation to obscure the timing measurement.
   • BImplement constant-time modular exponentiation so that execution time does not depend on the secret key bits.
   • CUse a larger RSA key size, such as 4096 bits, to make timing attacks impractical.
   • DPerform the RSA operation in a separate process to isolate the timing measurement.
   Reveal Solution Discussion Select an answer first
2. 22application · medium

   Your organization's mobile app uses TLS to protect data in transit, but a security review notes that the app does not validate the server certificate's hostname. What is the primary risk?

   • AThe app cannot connect to the server if the certificate has expired.
   • BThe encryption algorithm is weakened because the certificate is not checked.
   • CThe app becomes vulnerable to a padding-oracle attack.
   • DAn attacker can perform a man-in-the-middle attack by presenting a valid certificate for a different domain.
   Reveal Solution Discussion Select an answer first
4. 23application · medium

   A developer at your company implemented password hashing using a well-known library, but the code seeds the random salt with the current timestamp in milliseconds. After a security review, you must recommend a fix. What is the most appropriate action?

   • AReplace the timestamp with a cryptographically secure random number generator for the salt.
   • BUse a fixed salt across all users to simplify storage and verification.
   • CKeep the timestamp but hash it with SHA-256 before using it as the salt.
   • DIncrease the timestamp precision to nanoseconds to make it harder to guess.
   Reveal Solution Discussion Select an answer first
5. 24application · medium

   A web application uses CBC-mode encryption for session cookies. An attacker discovers that the application returns different error messages for valid and invalid padding. Which attack can the attacker perform, and what is the most effective mitigation?

   • ADowngrade attack; enforce TLS 1.3
   • BReplay attack; add a timestamp to the cookie
   • CBirthday attack; use a larger block size
   • DPadding oracle attack; switch to an authenticated encryption mode like AES-GCM
   Reveal Solution Discussion Select an answer first
6. 25application · medium

   A web server supports TLS 1.2 and TLS 1.3. A security scan recommends disabling TLS 1.2 because it allows cipher suites that are vulnerable to a specific attack. What is the most likely attack being mitigated?

   • AA padding-oracle attack that decrypts the session key.
   • BA downgrade attack that forces the client to use an older, weaker protocol version.
   • CA cache-timing attack that leaks the session ticket.
   • DA timing attack that reveals the server's private key.
   Reveal Solution Discussion Select an answer first