.NET Core Shared Cookies - .net-core

Question

I have .NET Core app with .NET Core Identity.
I've setup shared cookie into Startup.cs:
services.AddIdentity<User, Role>()
.AddEntityFrameworkStores<DataContext>()
.AddDefaultTokenProviders();
services.ConfigureApplicationCookie(options =>
{
options.Cookie.Name = ".AspNet.SharedCookie";
});
services.AddAuthentication()
...
app.UseAuthentication();
app.UseAuthorization();
Also I have 2nd .NET Core app where I don't have authentication at all but want to use just that SharedCookie and I did the following in the Startup.cs:
services.AddAuthentication("Identity.Application")
.AddCookie("Identity.Application", options =>
{
options.Cookie.Name = ".AspNet.SharedCookie";
});
...
app.UseAuthentication();
app.UseAuthorization();
and on controller actions I set attribute [Authorize].
I logged in into 1st app and go to 2nd app and see error /Account/Login... page doesn't exist.
Yes I don't have that page but why do I see this issue? Did I forget anything to add in my code?
And one more question: what's SharedCookie string? Is it random string or it's encoded some user data? can I extract any info from that SharedCookie, for example Id of User?

Answer 1

So my solution was to add DataProtection step to both apps:
if (!Env.IsDevelopment())
{
services.AddDataProtection()
.PersistKeysToFileSystem("{PATH TO COMMON KEY RING FOLDER}")
.SetApplicationName("SharedCookieApp");
}
And one more question: what's SharedCookie string? Is it random string or it's encoded some user data? can I extract any info from that SharedCookie, for example Id of User?
Yes, I can extract Id, Email of user in the following way:
var id = HttpContext.User.FindFirstValue(ClaimTypes.NameIdentifier);
var email = HttpContext.User.FindFirstValue(ClaimTypes.Email);