Email encryption

Keep your messages safe from prying eyes

I've been working on a large project related to internet security for the past couple of months. I've talked to dozens of people about the risks we face going online. This rabbit hole goes much deeper than I thought.

It seems to me that the internet made the leap from the lab to the high street before it was ready for the big time. The wonderful scientists and programmers who developed it had a better grasp of technology than of human nature. Let's take one example: email.

�The recipient has no way of proving that you sent it or that it hasn't been tampered with.�

When you send a message it goes through your computer, a company or ISP email server and a series of intermediate hops to traverse the internet before arriving at the recipient's ISP or email server and eventually their email client.

At any point, it can be read by anyone with the access and tools to inspect the servers or IP packets as they travel over the net. Not only that, but the recipient has no way of proving that you sent it or that it hasn't been tampered with en-route. In the jargon, there's no encryption, authentication, non-repudiation or integrity to email.

The epidemic of phishing emails, which pretend to come from banks and other trusted organisations, shows that authentication is as big an issue as encryption. A more robust email system would make spam a thing of the past. There are also Data Protection and client confidentiality issues to consider.

Yet, despite the risks, most people send and receive the most sensitive information imaginable by email.

Encrypted email

I've been looking at PGP Desktop 9.0 this week. I don't normally review products for this column so I'm going to use it as an example of a way of solving the email problem. Incidentally, PGP stands for Pretty Good Privacy.

It uses technology called public key encryption to encrypt and sign emails. That way the recipient of an encrypted email knows it hasn't been tampered with. It also means that nobody can read it except the intended recipient. This technology is similar to the encryption behind secure web pages.

If I send you an email in Microsoft Outlook 2003, PGP Desktop will automatically check to see if you have a public key registered on its key server. If you do, it'll encrypt and sign the email. If not, you get a plain text, unencrypted email as normal. It's completely painless and straightforward.

Back to the real world

Setting up an encrypted email system has taken me a few hours and to really understand what's going on behind the scenes will take a lot longer. Buying the software is expensive. PGP Desktop typically costs around �60 per user, although there are free open source equivalents such as the GNU Privacy Guard.

�If no-one uses encryption, who can I send encrypted emails to?�

Email benefits from the network effect. The more people use it, the more useful it is. However, because it is not widely used, email encryption suffers in comparison. If no-one uses encryption, who can I send encrypted emails to?

For the moment, I feel like a pioneer. Rumour has it that even the inventor of Pretty Good Privacy, Phil Zimmermann doesn't get too many encrypted emails. However, as people wake up to the risks of unencrypted email, I predict that encrypted email will become much more commonplace and routine.

What next?

Matthew Stibbe writes a new column every fortnight. Sign up to receive them automatically by email.