Rainbow tables are best described as which of the following?

• A. They are a type of encryption key.
• B. They are used to speed up hashing by caching key values.
• C. They are files containing many hash-to-plaintext mappings used to crack hashes
• D. They are used to compress data

Answer: (C)

Rainbow tables represent precomputed mappings from hashes back to plaintext passwords, created to speed up cracking password hashes. Instead of hashing every candidate password on the fly, an attacker looks up a given hash in a large table to find the corresponding password, if it’s included. This approach leverages the time–memory tradeoff by storing many hash-to-plaintext pairs and, in optimized setups, using chains to keep the table size manageable.

They’re not encryption keys, and they’re not a general method for speeding up legitimate hashing workflows. They’re also not a data compression technique. In practice, salting hashes (adding random data to each password before hashing) severely limits the effectiveness of rainbow tables, since each salt requires a separate table.