Access control to the website

Hello, I am a WP “newby” working on a website. For regulatory reasons I am only allowed to grant access to the website to those visitors who identify themselves (either by providing an e-mail address) or to those who got a password which I will provide upon request. Does anyone know of a plugin that serves this purpose? I have already searched for quite a long time but unfortunately without success. Maybe I am not searching right? Any assistance on this? Thank you so much for your assistance!! Regards, Marcel