Why is salt often added to hashing?

• A. To speed up the hashing process.
• B. To reduce the effectiveness of pre-computed rainbow table attacks.
• C. To allow the hash to be reversible.
• D. To replace the need for a robust hash function.

Answer: (B)

Salt adds randomness to the password input before hashing, so each user’s stored hash becomes unique even if the same password is used by multiple accounts. This is the key defense against pre-computed rainbow table attacks, which rely on matching a hash to a password across many common values. With a unique salt, an attacker would have to build a separate, enormous table for every possible salt, which is impractical. The other options don’t fit: salt doesn’t speed up hashing, hashing remains one-way and salt doesn’t make it reversible, and salt doesn’t remove the need for a strong hash function.