From what understand, SSL-Strip sits between the target user and the server, establishing a HTTPS connection between itself and the server, and an unsecured, plain old HTTP channel between itself and the target user.
What confuses me is, in a video demo of the tool, one of the prerequisites was an SSL certificate.
Why is the certificate required? Can't the "computer proxy acting as a fake user" send the plaintext back to the user without one? In fact, it seems the only reason a signed SSL certificate would be required would be if the middle-man sent back HTTPS encrypted data back to the user.