Which of the following is NOT a requirement for a valid password?

A valid password is typically designed to enhance security while being user-friendly. Requirements for a password can vary depending on the system or organization, but certain criteria are commonly implemented.

A password must contain a letter to ensure it includes a character from the alphabet, which prevents overly simplistic passwords. Similarly, including a number adds complexity, making it harder for unauthorized users to guess or crack the password. The stipulation that a password must be at least 7 characters long is a standard to ensure there is sufficient length, which contributes to overall security.

While uniqueness is indeed an important aspect of overall password management, it is not a technical requirement for the password itself to be considered valid in terms of length or character composition. Uniqueness typically refers to the idea that each user should have their own password that is distinct from others, but it does not affect the structural validity of a password as defined by length or character types. Therefore, the correct choice highlights a requirement that is important from a policy standpoint rather than a technical standpoint.