What is the purpose of adding salt to passwords?

Adding salt to passwords serves the purpose of enhancing the security of stored password hashes. When a salt—a random value unique to each password—is added, it complicates the hashing process by making the resultant hash distinct even for identical passwords. This means that if two users happen to choose the same password, their hashes will differ due to the unique salts, thus increasing the number of possible unique password hashes.

This approach effectively thwarts pre-computed attacks, such as rainbow table attacks, where attackers use pre-calculated tables of hashes for known passwords. By requiring the unique salt alongside the password for each hashing operation, it essentially increases the complexity for an attacker, making it significantly more difficult to crack passwords.

The other choices do not accurately address the purpose of salting passwords. For instance, shortening password length or enforcing plain text storage detracts from security, while efficient encryption is not the key focus of salting; rather, salting relates to hashing. Thus, using a salt is a critical practice in modern password management to bolster security against various forms of attacks.