There is an interesting concept that surfaces sometimes in business, politics or espionage called “Plausible deniability”.  It involves the creation of chains of command that are loose enough to untie when the need arises.  If high ranking officials or politicians become aware of disreputable or questionable activities, they may claim, using “Plausible deniability”, that there is no  way of proving they had any knowledge of such activities.  They can simply deny it, and since there is no direct connection to these high ranking officials, there can be no hard evidence linking themselves to the questionable activity or to the knowledge thereof.  The Plausible deniability concept is also applicable in technology, as you”ll see.

There is this great open-source encryption  software that you can install for free called Truecrypt.  Since most people have bank statements or other sensitive files stored on their computers, this program is for everyone.   You can easily set up what they call an “encrypted volume”.  What is that?  It looks just like any of your letter drives on your computer, but it is really a container of all your encrypted documents.  You can drag your sensitive files right into this new drive and use it just like any other drive, ie: drive F: on your computer.  Truecrypt performs “on the fly” encryption which means that your file is encrypted and decrypted in memory as you use work with it.    When you are done updating a file, it is always written back to the volume encrypted so you never have to worry!

When you mount a Truecrypt volume you need to enter your password and when the computer shuts down down the volume is then unmounted.  If you look at the file that is used to mount these encrypted volumes you’ll see random bits of data.  There is absolutely no way to get any information about your data stored on the encrypted file; it’s just random noise.  To give you an idea of how safe your data is, Truecrypt writes on their website:

“The only way to recover your files is to try to “crack” the password or the key, but it could take thousands or millions of years depending on the length and quality of the password/keyfiles, on software/hardware efficiency, and other factors.”

These guys really covered everything, so it is a highly secure system.  Truecrypt volumes are extremely easy to set up and their website is a great resource for how to get started and learn more about how this technology works.

Back to Pluasible deniability.  Let’s say that I created an encrypted volume and put some very sensitive files in my encrypted container, all is good and my data is quite safe.  Now let’s suppose that some evil  person gains access to your  computer and forces you to give over your secret files he thinks you have.  He knows that you’re smart and that you must have encrypted your sensitive data.  You have no choice but to give him your password and he then can take your files!  To get around this scenario, Truecrypt allows you to create a hidden volume.  A hidden volume is an encrypted volume within another encrypted volume, each having different passwords.  Now, in the case of the evil person, you can say to him “here are my secret files” and give up the password to the outer volume.  The files you “gave” him in the outer volume are not really your sensitive files.  The inner volume contains the truly secret files.  When you open up the outer volume there is absolutely no way of knowing that there is a hidden volume inside.  You have successfully invoked “Plausible deniability” in the sense that your adversary does not know anything other than that outer volume exists and you do not “have” any secret files the adversary wants.  The direct link was severed and you can deny any knowledge of those files.

In a future post we”ll talk about whole disk encryption a new feature of truecrypt. This solution is perfect for laptops or even desktops that contain sensitve data.

Bruce Shneier posted a fascinating article here. Tor allows you to be anonymous on the Internet. The challenge of anonymity on the Internet is an interesting problem we don’t often think about. The Internet was not designed to allow us to be anonymous. We know that all machines connecting to the Internet have a unique IP address. You’ll say, “that doesn’t tell anyone my name or the name of my company”. However, it does uniquely identify your traffic on the Internet. If you connect to a website your computer is actually connecting to a server (like we saw in the Netstat posting). The server wants to send back the web-page you just requested. The server knows you by the connection that you just established, and can send back the page you requested. So the server must know your IP, which, today is typically the IP of your router. Still, this IP identifies you or your household whether you like it or not; there is no and ifs or buts about it. You can imagine that there are people out there that are adamant about wanting to be private on the Internet. Perhaps they have nefarious reasons and that’s why they want anonymity. Others just don’t want websites or ISP’s knowing what they do on the Internet.

So Tor (the onion router) provides anonymity for people. It’s a highly complex system. In a very short explanation, your traffic is bounced between a number of Tor routers that are in different locations all over the world. The traffic is encrypted between each Tor router. After the traffic is bounced between the Tor routers it exits the last Tor router and is then routed normally on the Internet. The website whose server you connected to serves the web-page page back to that last TOR router, and it travels back path through all those TOR routers back to you. The only Ip that the server actually knows is the IP of the last Tor router - not your IP address. This solution is extremely robust. If any of the Tor routers were compromised they still would not reveal any information about your traffic due to the encryption scheme that is used between Tor routers.

This security researcher ran his own Tor exit nodes for an experiment. By examining the traffic (also called “sniffing”) on his TOR router, he ended up seeing many email log-on credentials, as well as other log-on information of Tor users. Some of these users were government agencies in Third World countries, and also corporate account credentials. These people using TOR did not understand what the real purpose of TOR actually is. Tor allows you to use the internet anonymously, by encrypting traffic within the Tor network. However, it ultimately needs to exit onto the internet. When it does exit, the traffic is routed in the clear, so it does not, in any way, encrypt traffic leaving the exit node. If you want to be secure you will need to use an ‘end to end’ encryption solution like SSL. Anonymity does not mean privacy. I like the analogy he uses with Alchoholics Anonymous.