Tryit Editor v1.8

Source Code:

<!DOCTYPE html>
<html>
<body>

<form action="demo_keygen.asp" method="get">
  Username: <input type="text" name="usr_name">
  Encryption: <keygen name="security">
  <input type="submit">
</form>

<p><strong>Note:</strong> The keygen tag is not supported in Internet Explorer.</p>

</body>
</html>

Result:

W3Schools.com - Try it yourself

Edit the code above and click "Submit Code" to see the result.