title: Maintain passwords while switching from ASP.NET Membership to ASP.NET Core Identity
body: <p>My company is planning to upgrade our applications from .NET Framework to .NET Core, and as part of that to upgrade from ASP.NET Membership to ASP.NET Core Identity server. I found a useful article on this <a href="https://docs.microsoft.com/en-us/aspnet/core/migration/proper-to-2x/membership-to-core-identity?view=aspnetcore-2.2" rel="nofollow noreferrer">here</a>.</p>
  
  <p>However, there is a sub-note with massive implications:</p>
  
  <blockquote>
    <p>After completion of this script, the ASP.NET Core Identity app created
    earlier is populated with Membership users. Users need to change their
    passwords before logging in.</p>
  </blockquote>
  
  <p>We can't ask 600,000 users to change their password as part of this migration. However, the membership passwords are one-way hashed, so we can't retrieve them and then migrate them. So I'm wondering how we would go about maintaining our existing users' passwords with the new Identity Server approach.</p>