Rainbow Tables and Password Cracking ECES Practice Questions (Page 5)

Questions 21–25

1. 21application · medium

   A developer is creating a rainbow table for a password set of 8-character lowercase alphabetic passwords (26^8 possibilities). To reduce the table size, the developer decides to use longer chains. What is the primary trade-off of increasing chain length?

   • ALonger chains reduce both storage and lookup time.
   • BLonger chains have no effect on storage or lookup time.
   • CLonger chains reduce the number of stored endpoints but increase the average lookup time.
   • DLonger chains increase the number of stored endpoints but decrease lookup time.
   Reveal Solution Discussion Select an answer first
2. 22foundation · easy

   What is the primary purpose of a rainbow table in password cracking?

   • ATo store precomputed hash-to-password pairs for fast lookup
   • BTo generate random passwords for brute-force attempts
   • CTo identify the hash algorithm used by a target system
   • DTo encrypt passwords before storing them in a database
   Reveal Solution Discussion Select an answer first
4. 23expert · hard

   A penetration tester is using a rainbow table to crack a set of NTLM hashes. The table was generated with a chain length of 10,000 and a reduction function that maps 128-bit hashes to 8-character alphanumeric passwords. During the lookup process, the tester finds a matching endpoint in the table but the reconstructed chain does not produce the target hash. What is the most likely cause?

   • AThe reduction function is not deterministic.
   • BThe password is longer than 8 characters.
   • CA merge or collision occurred, causing the chain to converge with another chain and the endpoint to match a different starting point.
   • DThe hash algorithm used for the table is different from NTLM.
   Reveal Solution Discussion Select an answer first
5. 24application · medium

   A developer is building a rainbow table for a password set consisting of all 6-digit numeric PINs (000000–999999) hashed with MD5. The developer wants to minimize the table size while keeping the lookup success rate high. Which design choice best achieves this goal?

   • AUse a reduction function that maps hashes to random 128-bit values.
   • BUse a single long chain with a length of 1,000,000 and store only the start and end points.
   • CUse multiple chains of length 1000 with a reduction function that maps hash outputs back to the 6-digit PIN space.
   • DStore every hash and corresponding PIN in a simple lookup table.
   Reveal Solution Discussion Select an answer first
6. 25application · medium

   A developer is implementing a rainbow table generator for a CTF challenge. The table must cover all 6-character numeric passwords (10^6 possibilities). The developer wants to minimize the table size while keeping the lookup time acceptable. Which design choice best achieves this?

   • AUse a single reduction function for all chains to simplify the implementation.
   • BStore every possible hash in a sorted list for direct lookup.
   • CGenerate multiple chains, each with a different reduction function, and store only the start and end points of each chain.
   • DUse a single hash chain with a very long chain length and store only the start and end points.
   Reveal Solution Discussion Select an answer first