>>Hi,
>>
>>In a program that uses Sing-Factor Authentication (user ID and Password) I understand that each ID has to be unique. Does each user Password have to be unique too or duplicates are allowed?
>>
>>TIA
>
>If you make a unique password, alerting the user that that password is used by another user,
>indirectly you're helping to get into other people's homes.

LOL!, and the system can even tell you: Hey! your password is already used by John! :D

Could be funny xD