This article will describe the implementation of a security stamp property for a user. I will assume you have downloaded the ASP.NET Core 3.1 - Users Without Identity Project or created a new ASP.NET Core 3.1 Razor Pages project. See Tutorial: Get started with Razor Pages in ASP.NET Core. You should review the earlier articles of the Users Without Identity Project series.

UWIP v2 implements a SecurityStamp property for the AppUser.

Entities > AppUser:

[Required]
[StringLength(32)]
[Display(Name = "Security Stamp")]
public string SecurityStamp { get; set; }

When a new AppUser is created, the SecurityStamp is set with a GenerateSecurityStamp method.

Services > TokenService:

public string GenerateSecurityStamp()
{
    byte[] bytes = new byte[20];
    RandomNumberGenerator.Fill(bytes);
    return Base32.ToBase32(bytes);
}

The project implements a CreateUserPrincipalAsync function in SignInService.cs. The ClaimsPrincipal employs a security identifier claim (ClaimTypes.Sid) with the SecurityStamp value.

Services > SignInService:

private async Task<ClaimsPrincipal> CreateUserPrincipalAsync(int appUserId, string authenticationMethod)
{
    var appUser = await _userService.GetAppUserByIdAsync(appUserId).ConfigureAwait(false);
    var claims = new List<Claim>
        {
            new Claim(ClaimTypes.NameIdentifier, appUser.Id.ToString(), ClaimValueTypes.Integer),
            new Claim(ClaimTypes.Name, appUser.LoginName),
            new Claim(ClaimTypes.Sid, appUser.SecurityStamp),
            new Claim(ClaimTypes.AuthenticationMethod, authenticationMethod),
            new Claim(UWIPConstants.TwoFactorEnabledClaimType, appUser.TwoFactorEnabled.ToString())
        };

    if (appUser.AdministratorRole)
        claims.Add(new Claim(ClaimTypes.Role, UWIPConstants.AdministratorRole));
    if (appUser.MustChangePassword)
        claims.Add(new Claim(UWIPConstants.MustChangePasswordClaimType, string.Empty));

    var applicationIdentity = new ClaimsIdentity(claims, UWIPConstants.ApplicationScheme);

    return new ClaimsPrincipal(applicationIdentity);
}

The CookieValidator has been updated to validate the current SecurityStamp against the ClaimsPrincipal's ClaimTypes.Sid claim.

Services > Middleware > CookieValidator:

private static async Task<bool> ValidateCookieAsync(CookieValidatePrincipalContext context)
{
    var claimsPrincipal = context.Principal;
    var nameIdentifier = claimsPrincipal.Claims?
        .Where(c => c.Type == ClaimTypes.NameIdentifier)
        .Select(c => c.Value)
        .FirstOrDefault();

    if (!int.TryParse(nameIdentifier, out int appUserId)) return false;

    var securityStamp = claimsPrincipal.Claims?
        .Where(c => c.Type == ClaimTypes.Sid)
        .Select(c => c.Value)
        .FirstOrDefault();

    if (string.IsNullOrEmpty(securityStamp)) return false;

    var userService = context.HttpContext.RequestServices.GetRequiredService<IUserService>();
    return await userService.ValidateAppUserSecurityStampAsync(appUserId, securityStamp).ConfigureAwait(false);
}

The SecurityStamp is also used to generate and validate email confirmation and password reset tokens.

Update 02/23/2021

I updated the article links.