Need help with new plugin: post passwords

Hey all. I need some help on the idea side of things, rather than the coding, for once.

I’m working on my very first plugin, called “Post OTP,” which will allow the use of one-time passwords (passwords that delete themselves after the first use) on password-protected posts. I’ve got the admin side functioning pretty well – admin can view passwords both active and used, as well as generate new passwords for new visitors. These passwords are stored in the database along with the name of the person to whom they are assigned.

Now I need to make the passwords actually WORK, and I’m not sure how to go about it. Can you help me with how to “break into” the post password functionality?