Diffie-Hellman Key Exchange and Random Number Generators ECES Practice Questions (Page 4)

Questions 16–20

1. 16application · medium

   A security auditor is reviewing a system that uses a Mersenne Twister to generate random numbers for Diffie-Hellman key exchange. The auditor flags this as a vulnerability. Which property of the Mersenne Twister makes it unsuitable for cryptographic use?

   • AIt requires a hardware entropy source to operate, which is not available in the system.
   • BIt produces only numbers that are multiples of a fixed constant.
   • CIt is too slow for generating the large numbers needed in Diffie-Hellman.
   • DIts output is deterministic and can be predicted if enough consecutive outputs are observed.
   Reveal Solution Discussion Select an answer first
2. 17foundation · easy

   What is the potential impact of using a weak random number generator to generate Diffie-Hellman private keys?

   • AAn attacker may be able to predict the private keys and compute the shared secret.
   • BThe shared secret will be shorter than expected.
   • CThe key exchange will fail to complete.
   • DThe public values will be identical for all users.
   Reveal Solution Discussion Select an answer first
4. 18foundation · easy

   Why is the Mersenne Twister PRNG considered unsuitable for cryptographic use?

   • AIt produces a predictable sequence after observing 624 consecutive outputs.
   • BIt requires too much memory to be used in embedded systems.
   • CIt does not produce a uniform distribution.
   • DIt is too slow for cryptographic applications.
   Reveal Solution Discussion Select an answer first
5. 19expert · hard

   A network administrator is configuring Diffie-Hellman key exchange for a VPN. The administrator wants to prevent man-in-the-middle attacks but also needs to minimize the computational overhead on the VPN gateway. Which approach best balances security and performance?

   • AUse digital signatures for authentication, which is more secure but adds significant computational overhead.
   • BUse authenticated Diffie-Hellman with pre-shared keys, which adds minimal overhead compared to digital signatures.
   • CUse a static Diffie-Hellman key pair to avoid the need for authentication.
   • DUse unauthenticated Diffie-Hellman with a large prime to increase security.
   Reveal Solution Discussion Select an answer first
6. 20foundation · easy

   Which attack is Diffie-Hellman key exchange particularly vulnerable to if no authentication is used?

   • ABrute-force attack on the shared secret
   • BReplay attack
   • CSide-channel attack
   • DMan-in-the-middle attack
   Reveal Solution Discussion Select an answer first