Rainbow Tables and Password Cracking ECES Practice Questions (Page 7)

Questions 31–35

1. 31expert · hard

   A security team is evaluating whether to use rainbow tables to crack a database of unsalted MD5 hashes. The passwords are known to be 8-character random alphanumeric (62^8 ≈ 2.18 x 10^14). The team has 10 TB of storage and a week of compute time. Which conclusion is most accurate?

   • ASalting the hashes would make rainbow tables more effective.
   • BA rainbow table with 10 TB of storage can cover a small fraction of the key space, but the success rate will be low.
   • CBrute force with a single GPU is faster than generating a rainbow table.
   • DA rainbow table covering the full key space is feasible with 10 TB of storage.
   Reveal Solution Discussion Select an answer first
2. 32foundation · easy

   What is the primary purpose of key stretching in password storage?

   • ATo make each password hash unique
   • BTo encrypt the password with a secret key
   • CTo increase the computational cost of hashing, slowing down brute-force and rainbow table attacks
   • DTo compress the hash to save storage
   Reveal Solution Discussion Select an answer first
4. 33expert · hard

   A security team is tasked with cracking a set of 500 unsalted MD5 hashes from a legacy system. The team has a server with 2 TB of storage and 7 days of compute time. They are considering building a rainbow table for the 8-character alphanumeric keyspace (62^8). Which approach is most practical given the constraints?

   • AUse a brute-force attack over the full 62^8 keyspace using the 7-day compute window.
   • BBuild a simple lookup table of all 62^8 hashes and store it on the 2 TB disk.
   • CUse a dictionary attack with a large wordlist and rule-based mutations.
   • DBuild a rainbow table covering the full 62^8 keyspace with a high coverage probability.
   Reveal Solution Discussion Select an answer first
5. 34foundation · easy

   Which of the following best describes the structure of a rainbow table?

   • AA database of cracked passwords collected from previous breaches
   • BA list of plaintext passwords with their corresponding hashes
   • CA sorted array of all possible hashes for a given character set
   • DA set of hash chains that start and end with plaintext values
   Reveal Solution Discussion Select an answer first
6. 35application · easy

   An analyst is using RainbowCrack to crack a set of LM hashes from a Windows system. The analyst has a rainbow table file for LM hashes but is unsure whether the table covers the specific password. Which step should the analyst take first to determine if the table is useful?

   • ARun the rainbow table lookup tool (rcrack) against the hash file and observe whether it returns a match.
   • BManually compute the reduction function for the hash and compare it to the table's endpoints.
   • CConvert the LM hash to an NTLM hash and use an NTLM table instead.
   • DCheck the file size of the rainbow table to estimate the keyspace coverage.
   Reveal Solution Discussion Select an answer first