PGP allowed technologists to encrypt the contents of their emails, and to sign the emails in a way that allowed them to prove the mail’s source was tied to a specific cryptographic key, held by a specific person. And with that, a power that was once the purview of nation-states became something determined hobbyists could do.

This kicked off what came to be known as the First Crypto War of the 1990s, a debate over who could use cryptography, and how, on the net. After an investigation of Zimmerman, with many lawyers and security researchers and corporations getting involved, the government backed down and stopped restricting encryption. New forms of cryptographic communication were born, allowing e-commerce and web services and online messaging to come into being. None of those things, and consequently very little of the net we know now, could have happened otherwise. This is because when everything is like email, you can’t trust what arrives at your computer. Without that trust, you can’t log in to anything, use your credit card, or even be sure that the information you have from trusted sources hasn’t been altered on its way to you. The CDC website could tell you to smoke more, the front page of The New York Times could be wishing your co-worker a happy birthday, the White House website could be announcing that the intercontinental ballistic missiles were on the way. Cryptography allowed for the possibility of trust on an open network.



Around the same time that PGP was released, two computer scientists, Nathaniel Borenstein and Ned Freed, created a way to extend what email could do. They created a scheme called MIME (Multipurpose Internet Mail Extensions) to let regular old email add new and strange features as people wanted them. By 1995, one of those features was S/MIME, which did the same essential things—encrypting and authenticating—as PGP did. MIME let you specify something you wanted email to do, and if people wrote support for it into the code of email clients, then it became something email could do. Other MIME extensions let you attach files to emails, and tell the computer what to do with them: open this one in Word, play that one as a movie. But none of these things changed email, they just piled more on top of it, extending and overloading the metaphors built into the basic technology people used for talking to each other online. Eventually when the web came along, and MIME standards and code let email turn into a full-fledged web browser, along with a calendaring app, a chat program, and the way you manage your identity online. All of this without ever doing much about the possibility that sneaky people were getting at your emails, or dealing with those mails from God or Santa Claus.

That brings us back to last week, and the release of Efail. The hack is simple and brilliant: It uses the fact that your email client thinks it’s a web browser. An attacker sending mail can steal the content of secret messages you may have sent or received. It works like this: An email client running OpenPGP (the current standard of PGP) or S/MIME decrypts messages when it receives them, and since the clients are also web browsers, they fetch things from the web for displaying them to you in the email you open at the same time. So what if you happened to open an email, which decrypts whatever message it may have inside, even a hidden one, while the same email also tells your email client to fetch an image off the web whose name is now the entire contents of a message it just decrypted? It would just do it, invisibly, sending the now easily readable message anywhere on the net without you ever knowing it happened. Sure, an image named “Meet me at the park on Sunday at 3 a.m. and we’ll make plans from there come alone.jpg” would never load on your screen, but you’ll have invisibly asked for it, and that ask will now be recorded in whatever computer out there the person who sent the mail wanted it recorded on. And that mail could have just as easily said it was from your spouse or boss as God or Santa Claus.