Fixing the Holes

The following is the second post in a series entitled, “Securing your Email.” Throughout the post, I am going to be referencing an analogy about mailing a letter that I described in the first post of the series. If you’re not familiar with it, you may want to take a minute to read it. I’ll wait…

There are a number of ways you can make email a more secure form of communication. One of the easiest ways to start patching holes in your current system is to look for major lapses in security and take care of those first. In my analogy, multiple security threats could be effectively eliminated by handing your postcard directly to the mail carrier and having your boss’ mail carrier hand it directly to him or her. That way, the postcard is never left sitting in an insecure location. There’s no chance for a random person walking down the street to read, copy, or change your message. If you really trust your postal workers and your message doesn’t contain too much sensitive information, this may be all the protection you need.

The equivalent in the email world is making sure you do all of your communication to and from your email provider over a secure connection. This is actually really easy to do, as long as your email provider supports it. Since GMail is fairly ubiquitous these days, I’ll use them as an example.

You want to make sure you’re viewing, sending, and receiving email over a secure connection. If you’re using a web browser to access GMail, you just need to make sure you log in using https://gmail.com (note the https). GMail also intelligently offers an option to “Always connect using https,” which makes sure you never forget and leave a postcard sitting out by the curb. I highly recommend enabling that option if you haven’t already. If you’re using a desktop mail client like Outlook or Thunderbird to access your email, make sure you specify a TLS or SSL connection when you’re setting up your account. By making sure the connection to and from your email service is secure, you’ve eliminated a major lapse in email security. Since many email services offer (or even require) it, it’s a good idea to get into the habit of verifying that you’re communicating over a secure connection whenever you check your email. It’s also imperative that you’re using a secure connection if you’re emailing on public networks, especially insecure wireless networks.

But what if your email service doesn’t offer secure connections? Or what if that’s not enough? Personally, I don’t think it is! If you look back to my analogy, you’ll see that there are still a number of prominent security threats. For example, what if some nefarious character at the post office tampers with your message?

The best way to deal with the remaining threats is using public-key cryptography. This is a fairly complicated topic, and I’ll only be scratching the surface of it in my posts. For now, let’s say that all you need is a file on your computer called an encryption key. In future posts, I’ll briefly cover how to obtain and use an encryption key and some of the basic theory behind public-key cryptography. For now, let’s understand some of problems that public-key cryptography aims to solve.

Flickr: Zappowbang's "Seal"

Flickr: Zappowbang's Seal (CC-BY)

In my analogy, I pointed out that upon receiving your message, your boss has no way to verify whether you were the original author. In the real world, a person uses their written signature to symbolize a document’s authenticity. Unfortunately, forged signatures are sometimes difficult to spot, except by experts. To provide an extra layer of verification, important documents that have been authenticated usually bear a seal. In the old days, many important people sealed their letters using some wax that they would impress with a unique design. This ensured the recipient that a document had not been tampered with en-route. Today, an official document whose signature was verified by a notary public also bears a seal. A digital signature is similar to a seal. It asserts that all (or part) of an electronic document was verified by the signer and that it has not been tampered with en-route. Since the documents are electronic, this makes a digital signature much more portable than a paper document bearing a seal. Unlike a wax-sealed message, digital signatures do not prevent anyone who comes across the message from reading or copying it. It is simply a indicator of the author’s authenticity.

Flickr: timg_vancouver's Engima Machine (CC-BY-SA)

Flickr: timg_vancouver's Engima Machine (CC-BY-SA)

If you need to send a message that contains extremely private information, which no one but the intended recipient must see, the message needs to be encrypted. As you can probably guess, this is means that even if someone were to examine the message text, they would not be able to read it. For example, the Enigma machine was used by the Germans in World War II to encrypt messages between their armies. An encrypted message contains a long string of seemingly random letters and numbers that have been disguised using a code. Messages are encoded so that only a person who has the proper key can unlock the code and reveal the original message. This is starting to sound a bit like a Dan Brown novel, isn’t it? Aside from that, encryption is kind of boring. It does its job really well, and as long as you pick an adequate passphrase for your encryption key, your information is fairly secure. Just make sure the Allies don’t capture your Enigma machine, or you might be sunk. 🙂

My purpose here is not to convince everyone to start using public-key cryptography to digitally sign or encrypt all of their emails. My purpose is to help you understand how insecure your email is and why this extra security is used and ultimately necessary in a lot of situations. Many of us have come to rely heavily on email as form of communication. If you are one of those people, it may be time to reconsider how much trust you place in that system. The methods that I described in this post should help restore most of the trust you may have taken for granted in the past. Still, if I can get a handful of you to start digitally signing your emails when I’m through, I will consider that a victory.

Now that I spent almost this entire post talking about strange things like digital signatures and encryption keys, you might be fairly confused. Before things get any more technical, I wanted to help you understand why we use these things and how they work on a basic level. In my next installment in this series, I’ll discuss some of the theory behind public-key cryptography and how it’s used to create an extra layer of security on top of email by establishing your true electronic identity. In the future, I’ll also cover how to obtain or create an encryption key and how to use it. Then you’ll truly be on the road to secure messaging!

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