Securing your browsers: Internet Explorer

As third and last, I’ll show you how to secure your browser settings for Internet Explorer.

Internet Explorer is somewhat different because it doesn’t have it’s own settings for cipher suites. It gets those from the operating system. In Windows they are implemented in one of the SSPI’s namely SChannel. So to enable or disable cipher suites in IE, you need to enable or disable them in Windows.

First, let’s take care of the obvious. In IE there is an SSLv3 setting in the Advanced tab of the Internet Options. Uncheck this and IE will be POODLE-proof. SSL 2.0 should be unchecked by default.


Now, to disable cipher suites we could edit the registry. This is complicated and error prone, so we are going to use a tool. Download IIS Crypto here. I recommend version 1.6 GUI for .NET 4.0.

Start the tool with elevated privileges and have most of the work done for you by clicking the Best Practices button. You’ll have to Press the Apply button and restart for the changes to take effect.

I have edited the cipher suite order and put the ECDHE_ECDSA ciphers at the top of the list, followed by the ECDHE_RSA ciphers. I have tried disabling MD5 hashing but found that some applications for RDP were not working anymore. Disable every protocol before TLS 1.0 and every cipher suite above Triple DES 168. I tried disabling Triple DES 168, but some websites wont work anymore because they are not updated to use the newer Elliptic Curve cipher suites yet. Please test what works for you and post in comments.




As you can see, I disabled all TLS_DHE_DSS suites and the RC4 suite. I use the 3DES_CBC suite as a fallback suite.

I also disabled a few RSA SHA256 and RSA SHA384 suites because Microsoft released a bad patch. The IIS Crypto site also tells us to disable these:


This concludes my ‘series’ on how to secure your browser. It may be that these settings will be deprecated real soon. It might also be that you can use these safely for a few years. All depends on the progress and development in the field of cryptography. I will keep you updated.

Securing your browsers: Chromium, Google Chrome or Opera

It took some time for me to write this blog. It was supposed to deal with all three major browsers, but I could not make the time lately. I started a  four year Professional Education last year. Together with my more-than-full-time job I just could not find the time to post anymore. In the meantime POODLE came along and this post is almost outdated before it is even written. Or typed 🙂

I got my bachelor and are now in my second year, hurray! Now, because of an obligatory assignment from school, I am supposed to write six blog posts before January 2015. So this presented the opportunity to start writing again and break this big subject up in parts.

We’ll start with Chromium first. This is also applicable to Google Chrome and Opera. Here we go.

So, because of POODLE, this subject should have your attention. If it does not, be glad you stumbled upon this blog. To secure your browser from any unsafe or insecure settings while visiting HTTPS web pages, do the following:

  • Disable SSLv3 (this counters POODLE)
  • Disable RC4 cipher suites as much as possible
  • Disable SHA1 cipher suites as much as possible
  • Disable DES3 cipher suites as much as possible

I have been testing different settings myself for months now, and the problem is that disabling cipher suites which utilize SHA1 hashing or RC4 ciphers altogether probably is not a good idea. Why? Well, for one, Youtube will stop working. Yeah, really. It seems, when visiting Youtube over TLS, your video stream will use an RC4 cipher. It kind of makes sense because RC4 is the least CPU intensive stream cipher. But still it is weird coming from the company that works hardest of all to put old cipher suites to rest.

Denying cipher suites which use SHA1 hashing will probably stop you from being able to visit a minority of sites. You will have to read the error presented to you to recognise why you can’t see a particular webpage. Be aware of this.

Anyway, there aren not any check boxes to check or buttons to push in the GUI, so you have to use start up parameters to force Chromium, Chrome or Opera to comply with thesesecurity settings. Please note that WordPress does not like the double hyphen sign. It replaces it with a dash upon publishing. So replace the dash with two hyphens to make it work. To stop using insecure cipher suites, you will have to start your Chromium, Chrome or Opera executable with the following parameters:


To stop using SSLv3, you’ll have to use the parameter:


To do this, you’ll have to edit the shortcut you use to start your browser to let it read:

“<PATH TO>\chrome.exe or opera.exe” –cipher-suite-blacklist=0x0005,0x0004,0x002f,0xc012,0xc011,0x003c,0xc011,0x0032,0xc007,0xc00c —ssl-version-min=tls1

This disables many outdated cipher suites. You can find them by the hex code here. You should know, this does not disable SHA1 nor DES3 altogether. The TLS_RSA_WITH_RC4_128_SHA (RC4-SHA) and TLS_RSA_WITH_3DES_EDE_CBC_SHA (DES-CBC3-SHA) will stay enabled for fallback and compatibility (e.g. Youtube) issues.

You can test your browser and the cipher suites it uses here or here. It should be these:

TLS_RSA_WITH_AES_128_GCM_SHA256 (0x9c)

If you’re interested, these are all the parameters I currently use with my Chromium browser:

–cipher-suite-blacklist=0x0005,0x0004,0x002f,0xc012,0xc011,0x003c,0xc011,0x0032,0xc007,0xc00c —ssl-version-min=tls1 –flag-switches-begin –enable-async-dns –enable-download-resumption –enable-encrypted-media –enable-fast-unload –javascript-harmony –disable-pinch –enable-quic –use-simple-cache-backend=on –enable-spdy4 –disable-touch-drag-drop –enable-webgl-draft-extensions –ignore-gpu-blacklist –enable-lcd-text –num-raster-threads=4 –disable-origin-chip –save-page-as-mhtml –touch-events=disabled –flag-switches-end

OK, that’s that. I will post some instructions for Firefox and Internet Explorer soon.

Securing your HTTPS Apache 2.4 web server with correct parameters

Warning: Keep in mind this is an ongoing field that is quickly changing. Vulnerabilities in protocols and implementations are discovered daily. If you read this information in a few months or even weeks, things could be radically different.

The last few days I’ve been researching HTTPS connections from Apache 2.4 webservers. This research was sparked by the recent Hearthbleed bug in OpenSSL. I’ve been reading up on vulnerabilities, cipher suites, encryption and hashing methods ever since.

The general move to SSL certificates with a bitlength > 1024bit also fueled this research. Microsoft removed support for 1024bit root CA certificates from their Operating System through a patch in March 2014.

One particular website that has a lot of information is They host a nifty server test tool at When testing our production webservers, we got this very poor result. We got a C for supporting weak cipher suites. We were also not mitgated against the BEAST vulnerability. This was tested after we patched Hearthbleed.




As you can see in the first line, the server had no preference in cipher suite order. Why is this a problem you ask? With modern browsers you always use a newer cipher suite anyway. The point is that external parties (hackers) can force your web server to use an insecure cipher suite to communicate with them.

The most shocking to me was that we, as sysadmins, including me, never really gave much thought to this. The general idea is that you put an SSL certificate on your webserver and it’s secured. As with so many security related product, this assumption is dead wrong. The default ssl_mod settings are optimized for compatibility, not security. With our web servers getting 10 millions+ hits a month and providing privacy sensitive information, there wasn’t much thought needed to see this needed some serious attention.

After some time we came to the following requirements:

  • Create a config that is as secure as possible.
  • All common browsers should be able to connect to our websites securely. The highly unsafe IE browsers on the Windows XP platform included.
  • SSL3 must be supported for older browsers/platforms.
  • We must be mitigated against all know attacks, such as BEAST, CRIME, BREACH, Lucky Thirteen, padding attacks, renegotiation, etc.

This appeared to be quite a challenge. In the case of BEAST this deserved some special attention, because mitigating against BEAST is only possible using RC4 cipher suites in TLS1.0 and SSLv3 connections. Unfortunately the research in  cracking the RC4 encryption got a serious boost in March 2013.

After days of testing, I came up with the following:

  • Use Apache 2.4.7. This version does not allow the key exchange in Diffie-Hellman cipher suites to be less then 2048bit. It will use the bitlength of the SSL certificate but will use no less then 2048bit.
  • Use an Apache binary that is compiles against a recent version (1.0.1g) of OpenSSL lib. This will ensure the serving of ECDHE and ECDHE-ECDSA cipher suites.
  • Use a 4096bit SSL certificate. This will strengthen the DHE key exchange mechanism.
  • Specifically disable SSLv2 even though it is not supported anymore with recent OpenSSL libs.
  • Force the cipher suite order in mod_ssl.conf.
  • Use a specific, custom ciphers suite to satisfy your specific needs.
  • Use mod_socache_shmcb to allow session caching and session resumption.
  • Use the Strict-Transport-Security parameter in your Virtual Host config to support HSTS.

Cipher suites are selected on the following criteria in order of importance:

  • Prefer ECDHE-ECDSA cipher suites
  • Prefer ECDHE cipher suites
  • Prefer DHE cipher suites
  • Prefer GCM block cipher suites
  • Prefer CBC block cipher suites
  • Prefer SHA384 hashing
  • Prefer SHA256 hashing
  • Prefer SHA hashing
  • Prefer cipher suites which support Forward Secrecy
  • Prefer cipher suites with 256bit encryption
  • Prefer cipher suites with 128bit encryption
  • Prefer cipher suites with 112bit encryption

As you can see, encryption bit length is only a minor factor in this. Forward Secrecy preference is implicitly done by preferring the ECDHE and DHE cipher suites.

For us, this would result in the ssl_mod config:

SSLSessionCache shmcb:/var/cache/mod_ssl/scache(512000)
SSLSessionCacheTimeout 300
SSLProtocol -SSLv2 ALL
SSLHonorCipherOrder On
SSLCompression Off

And the httpd config:

<VirtualHost *:443>

Header always set Strict-Transport-Security “max-age=63072000; includeSubDomains”

Alternatively, you can choose not to support CAMELLIA en SEED ciphers with the following parameter:


It’s up for debate if TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA (DHE-RSA-DES-CBC3-SHA) and TLS_RSA_WITH_3DES_EDE_CBC_SHA (DES-CBC3-SHA) are still wanted. These create connections with 112bit cipher strength instead of 168bit which you may think. If you require 128bit, leave them out. the DHE-RSA-DES-CBC3-SHA cipher provides Forward Secrecy, so the key to decode one session, cannot be used for another session.

You might want to put TLS_DHE_RSA_WITH_AES_128_CBC_SHA (DHE-RSA-AES128-SHA) before TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA (DHE-RSA-DES-CBC3-SHA), but since it’s included in EDH+aRSA, you’ll have to write it out.

Above settings result in an A+ rated site with BEAST mitigation, Strict Transport Security (HSTS), Forward Secrecy with all common browsers and no RC4 in vulnerable cipher suites:


ssllabs-a-plusssllabs-protocol-detailsssllabs-handshake-simulation ssllabs-protocol-details-and-cipher-suites

If you are not interested in mitigating BEAST (as most browsers are patched), you could use the following order:


Again, CAMELLIA and SEED could be left out:


And explicit denial of all RC4 encryption might be preferable:


I would also advise leaving out the 112bit TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA (ECDHE-RSA-DES-CBC3-SHA) cipher suite:


This would result in all modern browsers/flatforms (IE in Vista and higher, Andriod 4.0.4 and higher, FireFox, Chrome and Safari) to use ECDHE cipher suites with 256bit encryption. The TLS_RSA_WITH_3DES_EDE_CBC_SHA (DES-CBC3-SHA) suite will be used for all exceptions. Also encryption with the potentially vulnerable RC4 cipher is prevented.


“Elliptic curve cryptography”
“Elliptic Curve DSA”
“Elliptic curve Diffie–Hellman”
“SSL/TLS Deployment Best Practices”
“Configuring Apache, Nginx, and OpenSSL for Forward Secrecy”
“RC4 in TLS is Broken: Now What?”
“Updated SSL/TLS Deployment Best Practices Deprecate RC4”
“SSL Labs Test for the Heartbleed Attack”
“SSL Labs: Stricter Security Requirements for 2014”
Session Resumption
“HTTP Strict Transport Security”
“Strong SSL Security on Apache2”
“Increasing DHE strength on Apache 2.4.x”
“OpenSSL cipher suites” This site runs Apache. It’s cipher suites are: “EECDH+ECDSA+AESGCM EECDH+aRSA+AESGCM EECDH+ECDSA+SHA384 EECDH+ECDSA+SHA256 EECDH+aRSA+SHA384 EECDH+aRSA+SHA256 EECDH+aRSA+RC4 EECDH EDH+aRSA RC4 !aNULL !eNULL !LOW !3DES !MD5 !EXP !PSK !SRP !DSS”. This server runs nginx. It’s cipher suites are: ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:HIGH:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!CBC:!EDH:!kEDH:!PSK:!SRP:!kECDH; This site uses mod_spdy voor Apache 2.4. mod_spdy.
chrome://net-internals/#spdy Monitor SPDY connections in the Chrome browser

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