Ensuring Privacy in your Personal and Professional Electronic Communications

In the past, if the government wanted to violate the privacy of ordinary citizens, it had to expend a certain amount of effort to intercept and steam open and read paper mail, or listen to and possibly transcribe spoken telephone conversations. This is analogous to catching fish with a hook and line, one fish at a time. Fortinuately for freedom and democracy, this kind of labor-intensive monitoring is not practical on a large scale. Today, electronic mail is gradually replacing conventional paper mail, and is soon to be the norm for everyone, not the novelty it is today. Unlike paper mail, e-mail messages are just too easy to intercept and scan for interesting keywords. This can be done easily, routinely, automatically, and undetectably on a grand scale. This is analogous to driftnet fishing-making a quantitative Orwellian difference to the health of democracy.-- Phil Zimmermann, Creator of Pretty Good Privacy (PGP)

Phil Zimmermann wrote that in the mid 1990's and it is even more true today in this post September 11th world. In this day when civil liberties are more readily being given up in an attempt to gain more security against terrorist threats the FBI is more likely to use tools like Carnivore. One of the more worrisome statements comes directly from the FBI's description of Carnivore: "The Carnivore device works much like commercial "sniffers" and other network diagnostic tools used by ISPs every day...". Your communications may possibly be intercepted by any number of individuals and corporations on it's way to it's final destination. Email experts describe the medium as being more like a postcard than a letter. With a postcard the very honest people do not read it, but even the honest people get curious and are tempted. The new Patriot Act passed in October 2001 gives the FBI the ability to tap into your electronic communications even if you are not targetted by an investigation.

But, I have nothing to hide...
While that may be true, it is entirely possible you are breaking the law without even knowing it. Many times innocuous things we do everyday might be unlawful without you even knowing it. For example trading MP3s is a very popular activity, but we all know it's illegal. If you were to admit to possessing illegally copied music over email it is conceivable that would be enough evidence for the FBI to get a search warrant. Even so, we frequently think of the communications we have with our friends, family and coworkers to be private and would like them to remain so. We often speak differently in private than we would in public. We often forget that emails, like postcards, are not private and can be read by any number of individuals. Another issue is your email can be stored or copied at any of the servers it passes through on it's destination. This leads to emails lasting much longer than intended. Lets take an example.

Lets say you sent a personal email to your best friend with an off-color joke. If you sent this email from work it is entirely possible that email was searched and logged. Even if you sent it from home it is still possible that your ISP or any of the servers that handled the emails packet's could read the email. Lets say you realized afterward that the email could be considered innapropriate and you asked your sibling to delete the message and you deleted it from your "sent messages" folder. The problem is that message continues to live on. That message can be living in a database somewhere forever. You don't know where it is and cannot ask for it to be deleted. Someday it could be brought up against you by your boss or in a court of law.

This issue of an uncontrollable message lifetime is the biggest problem. I have said things in the past that I wish I could have taken back or not said at all. This might be from youthful naivity or hightened emotions. In any case I would hate that in those occasions that my words had been permanently saved for posterity.

What do I do to protect the privacy of my e-mail?
The best protection is to encrypt your email. Encryption is the act of rendering your message unreadable to anyone but the intended recepient. Remember the decoder ring that came in the box of cereal? That was a type of encryption. Hopefully we'll be using stronger sorts of encryption on our emails, but you get the idea.

One type of encryption is symmetric encryption. That means it works both ways. I encrypt a message to you using a password. You have to know the same password to decrypt the message. The problem is how to communicate the password securely between the two parties. I cannot just send the password along the message because anyone could use to read the message. I would have to meet with the other party in person to tell them the password. This is usually not very convenient.

The solution to this problem is public key encryption. This uses a one-way encryption algorithm. I encrypt things in a manner that only a different key can decrypt it. So what I do is generate two keys. The key that can encrypt messages I give to everyone. The key that can decrypt them I keep only for myself. Anyone who wants to send me a message just encrypts it using the key I gave out (my public key) and only I can decrypt it using my private key. They would give me a private key so I could send them messages.

Without my private key, anyone intercepting messages intended for me would be completely unable to read them. This still leads to one problem.

Nobody can read my mail, but how do I securely know who sent it to me?
There exists a group of algorithms called hash algorithms. They are a function that takes some input and generates a value that represents the input, but the input cannot be recreated from the hash. Secure hash functions are functions that take an input (your message) and generate a unique output value (the hash) that uniquely identifies the message, but the message cannot be recreated from the hash. So now we have a unique way to identify the message. Finally we need a way to secure the generated hash. Since both the public and private key are one way ciphers anything encrypted with the public key can be decrypted by the private key (as in the above example). The reverse is also true. Anything encrypted with a private key can be decrypted by the public key. So here's a complete example:

I write a message to a friend. Upon completion I digitally sign the message by taking a secure hash of the message. I then take this hash value and encrypt it using my secret key. Now anyone who has my public key can use it to decrypt the hash and make sure it matches their independently generated hash value. By doing that they can be sure I wrote it because
1) Only I have my secret key and therefore I am the only one that can encrypt something that my public key can decrypt
2) Since the hash uniquely identifies the message then the message is exactly as I wrote it.
At this point anyone can determine that I was the author of the message and the message is exactly as I wrote it. It is the perfect digital signature. The last thing I do is encrypt the message with my friend's public key and send it to him.

What tools should I use?
Encryption tools for military and commerical uses have been around for the longest time. Only in 1991 when Phil Zimmermann decided to release PGP did individuals have a tool. Sadly marketing privacy to individuals has turned into a profitless venture so Network Associates has stopped offering PGP. Network Associates always offered a free version for individual use and those versions are still available:

A new tool is Gnu Privacy Guard. Created to provide an open source alternative to PGP it conforms to the OpenPGP standard. Like most open source software it is not as easy to use as it's closed source cousin. However it is more powerful because it supports more encryption algorithms (like the new Advanced Encryption Standard, AES). Also since it is still being worked on it will support new operating systems. Whichever platform you download from be sure to get the IDEA module to maintain compatibility with PGP.

GnuPG Download Page - Download GnuPG first
WinPT - A helper application for managing keys and easy encryption/decryption
GPGOE - A plugin for Outlook Express that greatly simplifies sending encrypted email

Other Resources:
Singh, Simon. The Code Book. New York, 1999. Anchor Books. Buy it on Amazon

-- Clinton Chadwick
-- cchadwick AT valleypond.net (replace AT with @ and remove spaces)
-- PGP Public Key