Modern Cryptographic Attacks ECES Practice Questions (Page 6)

Questions 26–30

1. 26foundation · easy

   Which of the following is an example of a side-channel attack surface in a cryptographic system?

   • AAn attacker measures the time taken to perform a private key operation to deduce key bits.
   • BAn attacker intercepts ciphertext and uses a padding oracle to recover plaintext.
   • CAn attacker tricks a client into using a weaker cipher suite during the TLS handshake.
   • DAn attacker exploits a buffer overflow in the encryption library to execute arbitrary code.
   Reveal Solution Discussion Select an answer first
2. 27foundation · easy

   What is the primary goal of a padding oracle attack?

   • ATo force a client and server to negotiate a weaker cryptographic algorithm.
   • BTo exploit a buffer overflow in the encryption library to execute arbitrary code.
   • CTo measure the time taken to perform a private key operation and deduce the key.
   • DTo recover the plaintext by repeatedly sending modified ciphertexts and observing whether padding is valid.
   Reveal Solution Discussion Select an answer first
4. 28application · medium

   A developer reuses the same nonce for multiple messages encrypted with AES-GCM. What is the most important consequence and the correct remediation?

   • AThe encryption becomes slower; switch to AES-CBC to improve performance.
   • BAn attacker can recover the authentication key and forge messages; the application must ensure nonces are never reused.
   • CThe key is weakened; rotate the key immediately and continue using the same nonce.
   • DThe ciphertext becomes larger with each message; use a larger nonce to avoid this.
   Reveal Solution Discussion Select an answer first
5. 29application · medium

   Your company's IoT devices use a custom protocol that encrypts each message with AES-CBC using a static key and a predictable initialization vector (IV) that increments by one for each message. What is the most critical risk?

   • AThe static key will eventually expire and cause a denial of service.
   • BAn attacker can recover the plaintext of messages by exploiting the predictable IV and CBC malleability.
   • CThe IV incrementing pattern makes the ciphertext larger over time.
   • DThe protocol is vulnerable to a padding-oracle attack because the IV is predictable.
   Reveal Solution Discussion Select an answer first
6. 30application · medium

   A developer is reviewing a web application that uses RSA encryption for sensitive form data. The code generates a new RSA key pair on every server restart and stores the private key in a world-readable configuration file. Which two implementation flaws are most directly exposed?

   • AProtocol downgrade and missing certificate pinning
   • BImproper key management and insecure key storage
   • CWeak random number generation and insufficient key length
   • DPadding oracle vulnerability and improper padding scheme
   Reveal Solution Discussion Select an answer first