Diamond.Captcha 2025.0.0

Diamond.Captcha Package

A lightweight and dependency-free Captcha generation package for ASP.NET Core. the Diamond.Captcha generates Captcha images entirely in-memory without relying on any external graphic libraries with zero dependency .

Features

• No external graphic library dependencies: Pure in-memory Captcha image generation.
• Supports two operational modes:
  • CachedCaptcha: Stores Captcha data in IMemoryCache.
  • DistributedCaptcha: Uses AES encryption to store Captcha data, enabling validation across multiple distributed servers.
• Easy to integrate with ASP.NET Core applications.
• Secure Captcha validation for both single-server and distributed environments.

How It Works

The Diamond.Captcha generates the Captcha image dynamically in memory and embeds the corresponding code in either:

• An in-memory cache for quick access and validation (CachedCaptcha).
• An encrypted token sent along with the response for stateless validation across distributed servers (DistributedCaptcha).

This design eliminates the need for external storage or graphic libraries and supports scalable, secure web applications.

Usage and Example

In Program.cs:

• Diamond.Captcha is enabled with the AddCachedCaptcha or AddDistributedCaptcha method.

using Microsoft.Extensions.DependencyInjection;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddCachedCaptcha();
//builder.Services.AddDistributedCaptcha(options => options.CryptographyKey = "YOUR_AES_KEY");

var app = builder.Build();

app.Run();

In HomeController.cs:

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Html;
using Diamond.AspNetCore.Html.Captcha;

public class HomeController : Controller
{
    private readonly ICachedCaptcha m_Captcha;

    public HomeController(ICachedCaptcha captcha)
    {
        this.m_Captcha = captcha;
    }

    [HttpGet]
    public IActionResult Index()
    {
        return this.View();
    }

    [HttpPost]
    [ValidateAntiForgeryToken]
    public IActionResult Index(string Captcha_RefID, string Input_Captcha)
    {
        if (this.m_Captcha.Validate(Captcha_RefID, Input_Captcha))
        {
            return this.Ok("Captcha validated successfully");
        }
        else
        {
            return this.BadRequest("Invalid Captcha");
        }
    }

    public IActionResult CaptchaImage(string id, int version = 0)
    {
        return this.m_Captcha.GetImage(id, version);
    }
}

In Index.cshtml:

@inject Diamond.AspNetCore.Html.Captcha.ICachedCaptcha captcha
@{
    string captchaRefID = captcha.NewRefID();
}

<form asp-antiforgery="true">

    <input type="hidden" id="Captcha_RefID" name="Captcha_RefID" value="@captchaRefID" />
    <input type="text" name="Input_Captcha" autocomplete="off" autocorrect="off" />

    <img id="CaptchaImage" src="/Home/CaptchaImage/@captchaRefID" />
    <a href="#" onclick="OnCaptchaRefresh()">Refresh</a>

    <script language="javascript">
        var version = 0;
        function OnCaptchaRefresh()
        {
            version++;
            var img = document.getElementById("CaptchaImage");
            img.src = "/Home/CaptchaImage/@captchaRefID?version=" + version;
            return false;
        }
    </script>
</form>

Links

• Sample

License

Apache-2.0 license