Login using existing logic in MVC 5

Question

Hi,

I have existing logic for login in a dll (say Login.dll) which takes the username and password and authenticate the user and returns  true/false based on user authenticated.

I am designing new ASP.NET MVC 5 application and I want to use this Login.dll to authenticate the user.

So in this case which Authentication I should use? I tried with Forms authentication but it has it's own logic and table structure to authenticate the user.

 

Can you please help me?