How does a library work without SecretKey?

[paulinhps]

I tried to create an authentication api without the secret key using the standard documentation on github.

My appsetting.json in Identity Provider Api

"AppJwtSettings": {
    "Issuer": "MyInssuerValue",    
    "Audience": "MyAudience" 
// SecretKey is missing
}

My Statup.cs in Identity Provider Api

 public void ConfigureServices(IServiceCollection services)
        {

            services.AddControllers();

            services.AddMemoryCache(); // Add this line

            services.AddIdentityEntityFrameworkContextConfiguration(options =>
                options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"),
                b => b.MigrationsAssembly(GetType().Namespace)));

            services.AddIdentityConfiguration();

            services.AddJwtConfiguration(Configuration)
                    .AddNetDevPackIdentity<IdentityUser>();
                    
            services.AddSwaggerConfiguration();
        }

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseSwaggerConfiguration();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthConfiguration();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
// [...]

In the other api that is authenticated by the identity provider I made the following settings:

My appsetting.json in Web Api

"AppJwtSettings": {
    "Issuer": "MyInssuerValue",    
    "Audience": "MyAudience" 
// SecretKey is missing
}

My Program.cs in Web Api

var builder = WebApplication.CreateBuilder(args);

builder.Services?.AddJwtConfiguration(builder.Configuration);
// more code

var app = builder.Build();

// middlewares
app.UseAuthConfiguration();
//more middlewares

app.Run();

And for every request the answer is the same:

 content-length: 0 
 date: Thu,28 Jul 2022 18:22:22 GMT 
 server: Kestrel 
 www-authenticate: Bearer error="invalid_token",error_description="The signature key was not found" 

But, if include SecretKey parameter works fine!