While I am pretty ignorant about the processes of encryption and decryption, I have become intrigued with the topic, particularly since the decision by the mail service companies Lavabit and Silent Mail to shut down their businesses rather than having to be forced to hand over the keys to the government to snoop on their clients’ emails.
Since the government has the power to impose a gag order that prevents the recipients from even acknowledging that they received the infamous National Security Letters demanding that they hand over information about specific people, there has been some speculation about exactly what Lavabit might have been asked to do.
Dan Goodin has some ideas about what they might have been asked. He says that Lavabit’s founder Ladar Levison designed the system keeping the draconian USA PATRIOT Act provisions in mind, to make it technically impossible for him to provide the government with information on individuals. Goodin describes the layers of encryption the system had built in.
But Levison was aware that there was a weakness.
All along, Levison spotted at least two ways his system could be subverted. The first was for an adversary to obtain the private key his server used to HTTPS encrypt the password and other sensitive data as it traveled between the user and the Lavabit server. The other was that Levison could somehow be forced to rewrite his source code and build a trap for users. For instance, Levison or anyone else with control over Lavabit might redesign the system so plaintext passwords were written to a log as soon as they were entered by the user, rather than being scrubbed from the system. Levison believed he had legal protections that would prevent the government from exploiting either weakness. After all, he had never heard of service providers being compelled to reveal the private key used to authenticate and encrypt HTTPS connections. Similarly, he was aware of no precedent mandating service providers change source code against their will.
Levison said he has always known Lavabit safeguards could be bypassed if government agents took drastic measures, or as he put it, “if the government was willing to sacrifice the privacy of many to conduct surveillance on the few.” For instance, if he was forced to change the code used when a user logs in, his system could capture the plain-text password needed to decrypt stored e-mails. Similarly, if he was ever forced to turn over the private encryption key securing his site’s HTTPS certificate, government agents tapping a connection could observe the password as a user was entering it. But it was only in the past few weeks that he became convinced those risks were realistic.
“I don’t know if I’m off my rocker, but 10 years ago, I think it would have been unheard of for the government to demand source code or to make a change to your source code or to demand your SSL key,” Levison told Ars. “What I’ve learned recently makes me think that’s not as crazy an assumption as I thought.”
Goodin says that in 2007, it seemed like the government actually did require an email service provider named Hushmail to take similar measures to obtain encrypted email messages.
The most recent NSA revelations suggest that these speculations are accurate.
It is still possible to defeat the NSA’s spying. As ProPublica reports,
The files show that the agency is still stymied by some encryption, as Mr. Snowden suggested in a question-and-answer session on The Guardian’s Web site in June.
“Properly implemented strong crypto systems are one of the few things that you can rely on,” he said, though cautioning that the N.S.A. often bypasses the encryption altogether by targeting the computers at one end or the other and grabbing text before it is encrypted or after it is decrypted.
Security analyst Bruce Schneier says that in its drive to commandeer the internet the US has betrayed the trust it was given as a steward of the internet and gives some advice on how to improve one’s security even in the face of the NSA.