diff --git a/mathcaptcha.php b/mathcaptcha.php
new file mode 100644
index 0000000..fd00523
--- /dev/null
+++ b/mathcaptcha.php
@@ -0,0 +1,107 @@
+<?php
+/**
+ * Name: Math-Captcha
+ * Description: This addon adds a smal calculation, which needs to be solved correctly before a new registration can be done
+ * Version: 0.1
+ * Author: Tobias Diekershoff <tobias@social.diekershoff.de>
+ * License: MIT style
+ **/
+
+use Friendica\App;
+use Friendica\Core\Hook;
+use Friendica\Core\L10n;
+use Friendica\Core\Renderer;
+use Friendica\Core\System;
+
+function mathcaptcha_install()
+{
+    Hook::register('register_form', 'addon/mathcaptcha/mathcaptcha.php', 'mathcaptcha_register_form');
+    Hook::register('register_post', 'addon/mathcaptcha/mathcaptcha.php', 'mathcaptcha_register_post');
+    Hook::register('template_vars', 'addon/mathcaptcha/mathcaptcha.php', 'mathcaptcha_template_vars');
+}
+
+function mathcaptcha_uninstall()
+{
+    Hook::unregister('register_form', 'addon/mathcaptcha/mathcaptcha.php', 'mathcaptcha_register_form');
+    Hook::unregister('register_post', 'addon/mathcaptcha/mathcaptcha.php', 'mathcaptcha_register_post');
+    Hook::unregister('template_vars', 'addon/mathcaptcha/mathcaptcha.php', 'mathcaptcha_template_vars');
+}
+
+/**
+ * Check if the captcha was solved correctly when posting the registration form
+ */
+function mathcaptcha_register_post(App $a, &$b)
+{
+    $solution = 0;
+    switch ($_SESSION['mathcaptcha_op']){
+            case 0:
+                $solution = $_SESSION['mathcaptcha_n1'] + $_SESSION['mathcaptcha_n2'];
+                break;
+            case 1:
+                $solution = $_SESSION['mathcaptcha_n1'] - $_SESSION['mathcaptcha_n2'];
+                break;
+            case 2:
+                $solution = $_SESSION['mathcaptcha_n1'] * $_SESSION['mathcaptcha_n2'];
+                break;
+        }
+    unset($_SESSION['mathcaptcha_n1']);
+    unset($_SESSION['mathcaptcha_n2']);
+    unset($_SESSION['mathcaptcha_op']);
+    $post = $b['post'];
+    if ($solution == $post['mathcaptcha']) {
+        return true;
+    } else {
+        notice(L10n::t('The solution for the captcha was incorrect'));
+        $a->internalRedirect('/register');
+    }
+}
+
+/**
+ * Add the captcha to the register form
+ */
+function mathcaptcha_register_form(App $a, &$b)
+{
+    $tpl = $b['template'];
+    $oldPath = $tpl->filename;
+    $newPath = 'addon/mathcaptcha/templates/register.tpl';
+    if (strpos($oldPath, 'theme') == true)
+    {
+        $theme = explode('/', $oldPath)[2];
+        $newThemePath = 'addon/mathcaptcha/templates/theme/'.$theme.'/register.tpl';
+        if (file_exists($newThemePath)) {
+            $newPath = $newThemePath;
+        }
+    }
+    if (file_exists($newPath)) {
+        $b['template'] = Renderer::getMarkupTemplate($newPath);
+        $b['template']->filename = $newPath;
+    }
+}
+
+/**
+ * add template variables to the registration template
+ */
+function mathcaptcha_template_vars(App $a, &$arr)
+{
+    // if the template currently processed is the register.tpl
+    // add some new variables to the list of template variables
+    if ($arr['template']=='register.tpl')
+    {
+        unset($_SESSION['mathcaptcha_n1']);
+        unset($_SESSION['mathcaptcha_n2']);
+        unset($_SESSION['mathcaptcha_op']);
+        $num1 = rand(1, 10);
+        $num2 = rand(1, 10);
+        $operator = rand(0, 2);
+        $_SESSION['mathcaptcha_n1'] = $num1;
+        $_SESSION['mathcaptcha_n2'] = $num2;
+        $_SESSION['mathcaptcha_op'] = $operator;
+        $ops = ['+','-','&times'];
+        $task = strval($num1)." ".$ops[$operator]." ".strval($num2);
+        $arr['vars'] = array_merge($arr['vars'], [
+            '$captchaTitle'=>L10n::t('Captcha'),
+            '$captchaDescription'=>L10n::t('In order to continue with the registration, please solve the following calculation.'),
+            '$mathcaptcha'=> ['mathcaptcha', $task, '', L10n::t('You have to type in the solution of the calculation'), 'required']
+        ]);
+    }
+}