Code for a browser Security Cookies

Here's an example of how you can use a security cookie to store and retrieve data related to user authentication:

<script>
  // Get the value of the security cookie, or create a new one if it doesn't exist
  var securityToken = getSecurityToken() || generateSecurityToken();
  
  // Send the security token with each HTTP request
  var xhr = new XMLHttpRequest();
  xhr.open("GET", "https://example.com/data");
  xhr.setRequestHeader("X-Security-Token", securityToken);
  xhr.send();
  
  function generateSecurityToken() {
    // Generate a random security token using the crypto API
    var array = new Uint8Array(16);
    crypto.getRandomValues(array);
    var token = "";
    for (var i = 0; i < array.length; i++) {
      token += ("00" + array[i].toString(16)).slice(-2);
    }
    // Set a cookie with the security token
    document.cookie = "securityToken=" + encodeURIComponent(token) + "; secure; HttpOnly; SameSite=Strict";
    return token;
  }
  
  function getSecurityToken() {
    // Get the value of the security cookie
    var cookies = document.cookie.split(';');
    for (var i = 0; i < cookies.length; i++) {
      var cookie = cookies[i].trim();
      if (cookie.indexOf('securityToken=') == 0) {
        return decodeURIComponent(cookie.substring('securityToken='.length));
      }
    }
    return null;
  }
</script>

In this example, we define a getSecurityToken() function that retrieves the value of a security cookie and returns it as a string. If the cookie doesn't exist, we return null.

We also define a generateSecurityToken() function that generates a random security token using the crypto API. We then set a cookie with the security token, using the secure, HttpOnly, and SameSite attributes to enhance the security of the cookie. We then return the token.

We then use the XMLHttpRequest object to send an HTTP request to https://example.com/data. We set the X-Security-Token header to the value of the security token, which allows the server to verify that the user is authenticated.

Note that in this example, we use the crypto API to generate a secure random number. This API is only available in modern browsers, so you may need to provide a fallback implementation for older browsers.