Bcrypt has the best kind of repute that can be achieved for a cryptographic algorithm: it has been around for quite some time, used quite widely, “attracted attention”, and yet remains unbroken to date. Bcrypt.Net makes it is usage in .NET land almost trivial. Check it out!
IdentityServer is a framework and a hostable component that allows implementing single sign-on and access control for modern web applications and APIs. The new IdentityServer4 is a real ASP.NET 5 application using all the standard platform facilities like DI, Logging, configuration, data protection etc, which means you have to learn less IdentityServer specifics than with previous versions.