What technique can be used to strengthen a weak password against brute-force attacks?

Key stretching is a technique specifically designed to enhance the security of weak passwords by making the process of brute-force attacks considerably more difficult. It works by taking a relatively weak password and applying a hashing algorithm multiple times, thus increasing the time it takes to compute and test each potential password during a brute-force attack. This means that even if a password is weak, the additional computational work required to crack it can effectively slow down an attacker.

Password hashing alone provides a level of security by converting the password into a different format, but it does not necessarily address the weaknesses of short or simple passwords when it comes to brute-force attempts. Two-factor authentication adds an extra layer of security by requiring a second form of verification, but it does not inherently reinforce the strength of the password itself. Account lockout mechanisms can help defend against repeated guessing attempts but do not directly make a weak password stronger. Key stretching thus stands out as a specific method to fortify weak passwords against brute-force attacks.