anchor.diff:  
   An appropriate value for the `nonceValiditySeconds` parameter of `DigestAuthenticationEntryPoint` depends on your application. Extremely secure applications should note that an intercepted authentication header can be used to impersonate the principal until the `expirationTime` contained in the nonce is reached. This is the key principle when selecting an appropriate setting, but it would be unusual for immensely secure applications to not be running over TLS/HTTPS in the first instance.
   
  -Because of the more complex implementation of Digest Authentication, there are often user agent issues. For example, Internet Explorer fails to present an "`opaque`" token on subsequent requests in the same session. Spring Security filters therefore encapsulate all state information into the "`nonce`" token instead. In our testing, Spring Security's implementation works reliably with FireFox and Internet Explorer, correctly handling nonce timeouts etc.
  +Because of the more complex implementation of Digest Authentication, there are often user agent issues. For example, Internet Explorer fails to present an "`opaque`" token on subsequent requests in the same session. Spring Security filters therefore encapsulate all state information into the "`nonce`" token instead. In our testing, Spring Security's implementation works reliably with Mozilla Firefox and Internet Explorer, correctly handling nonce timeouts etc.
   
   
   [[digest-config]]
  
positive.code: 
  ** `Cache-Control`, `Pragma`, and `Expires` - Can be set using the <<nsa-cache-control,cache-control>> element. This ensures that the browser does not cache your secured pages.
  ** `Strict-Transport-Security` - Can be set using the <<nsa-hsts,hsts>> element. This ensures that the browser automatically requests HTTPS for future requests.
  ** `X-Frame-Options` - Can be set using the <<nsa-frame-options,frame-options>> element. The http://en.wikipedia.org/wiki/Clickjacking#X-Frame-Options[X-Frame-Options ] header can be used to prevent clickjacking attacks.
  ** `X-XSS-Protection` - Can be set using the <<nsa-xss-protection,xss-protection>> element. The http://en.wikipedia.org/wiki/Cross-site_scripting[X-XSS-Protection ] header can be used by browser to do basic control.
  ** `X-Content-Type-Options` - Can be set using the <<nsa-content-type-options,content-type-options>> element. The http://blogs.msdn.com/b/ie/archive/2008/09/02/ie8-security-part-vi-beta-2-update.aspx[X-Content-Type-Options] header prevents Internet Explorer from MIME-sniffing a response away from the declared content-type. This also applies to Google Chrome, when downloading extensions.
  ** `Public-Key-Pinning` or `Public-Key-Pinning-Report-Only` - Can be set using the <<nsa-hpkp,hpkp>> element. This allows HTTPS websites to resist impersonation by attackers using mis-issued or otherwise fraudulent certificates.
  
negative.code: @RequestMapping("/messages/inbox")
  public ModelAndView findMessagesForUser(@AuthenticationPrincipal CustomUser customUser) {
  
  	// .. find messages for this user and return them ...
  }
  ----
  
  