Modern Cryptographic Attacks ECES Practice Questions (Page 3)

Questions 11–15

1. 11application · medium

   A penetration tester is assessing a legacy TLS 1.0 server that supports an outdated cipher suite. The tester successfully forces the client and server to negotiate the legacy protocol instead of the modern TLS 1.3 that both support. Which protocol-level weakness is being exploited, and what is the recommended remediation?

   • AKey reuse attack; rotate the server's certificate keys
   • BPadding oracle attack; update the server's padding implementation
   • CVersion rollback attack; disable all legacy protocol versions and cipher suites on the server
   • DTiming side-channel; implement constant-time decryption
   Reveal Solution Discussion Select an answer first
2. 12application · medium

   A VPN gateway supports both IKEv1 and IKEv2. A security assessment finds that an attacker can force the gateway to negotiate IKEv1 with a weak Diffie-Hellman group. Which attack is this, and what is the recommended configuration change?

   • AProtocol downgrade attack; disable IKEv1 and weak Diffie-Hellman groups on the gateway
   • BPadding oracle attack; update the encryption algorithm
   • CReplay attack; add anti-replay windows
   • DMan-in-the-middle attack; implement certificate authentication
   Reveal Solution Discussion Select an answer first
4. 13expert · hard

   A security auditor is reviewing a system that uses TLS 1.2 with a cipher suite that supports forward secrecy. The auditor must decide whether to recommend upgrading to TLS 1.3. The system must support legacy clients that do not support TLS 1.3. What is the most appropriate recommendation?

   • AUse TLS 1.3 but disable forward secrecy to improve performance.
   • BUpgrade to TLS 1.3 while maintaining TLS 1.2 with a forward-secrecy cipher suite for legacy clients.
   • CDisable TLS 1.2 entirely and require all clients to upgrade to TLS 1.3.
   • DKeep TLS 1.2 only because forward secrecy is already provided.
   Reveal Solution Discussion Select an answer first
5. 14expert · hard

   A startup is building a password manager. The developers want to use a strong key-derivation function (KDF) to protect user master passwords. They are considering PBKDF2 with a high iteration count, bcrypt, and Argon2id. The company must balance security against performance on a variety of user devices, including low-end mobile phones. Which choice is most appropriate?

   • AUse PBKDF2 with a very high iteration count because it is widely supported and simple.
   • BUse Argon2id with parameters that are memory-hard and configurable to fit the device's available memory.
   • CUse a simple SHA-256 hash with a salt because it is fast and does not burden low-end devices.
   • DUse bcrypt with a high cost factor because it is memory-hard and widely available.
   Reveal Solution Discussion Select an answer first
6. 15foundation · easy

   Which of the following is an example of a key management flaw that can compromise cryptographic security?

   • ARotating encryption keys on a regular schedule.
   • BStoring private keys in a password-protected file on the same server as the application.
   • CUsing a key derivation function (KDF) to derive encryption keys from a master key.
   • DRevoking a compromised certificate and issuing a new one.
   Reveal Solution Discussion Select an answer first