Connection string using Windows Authentication

Question

I'm building a website, however, I utilize Windows authentication in the database. I am aware that this is how you authenticate against SQL.

<connectionStrings> 
    <add name="NorthwindContex" 
       connectionString="data source=localhost;
       initial catalog=northwind;persist security info=True; 
       user id=sa;password=P@ssw0rd" 
       providerName="System.Data.SqlClient" /> 
</connectionStrings>

How can I change this so that Windows authentication will work with it?