He was talking about encryption, but also about "padded protocols" that would prevent intelligence agencies from discovering who was talking to who by analyzing Internet traffic, and mixed routing.
"We need non-attributable communications for unattributed internet access that is easy, transparent and reliable," he pointed out.
This is not the first time that Snowden asked coders to contribute.
One of the individuals who heard it and started doing something about it is Ladar Levison, the Texas-based owner of Lavabit, the encrypted email service once used by Snowden and 410,000 others. Lavabit has been shut down by Levison himself so that he would not "become complicit in crimes against the American people" by allowing the federal government access to his customers' emails and stored documents.
In the wake of the shutdown, Levison and encrypted communications firm Silent Circle have created the Dark Mail Alliance, a non-profit organization whose goal is to develop a private end-to-end encrypted alternative to email as we know it.
They have started working on Dark Mail, an open source transport protocol that would encrypt email metadata - subject line, email address of the sender and the recipient - so that intelligence agencies can't associate the two participants of the email exchange, and Levison launched a successful Kickstarter campaign to finance its development.
A version of the server software that supports the Dark Mail protocol has already been shipped to the most generous backers, and the binaries and code will reach the general public next month.
In the meantime, Levison has also presented the project at HOPE this weekend, and has shared more details about it.
The team that works on it is not big: Levison works on the protocol and the standard, and has hired talented software developer Stephen Watt to lead code development. A third paid member works alongside Watt, and there are also volunteers who contribute.
Watt is an unusual choice for this task if you consider his past: he has been sentenced to two years in prison for writing a piece of software for Albert GonzalesAlbert Gonzales, the infamous TJX hacker. But, according to Kim Zetter, Levison analyzed his legal case, and concluded that Watt did not commit a crime - he simply created software for an old-time friend, and wasn't involved in the cyber heist.
The Dark Mail project is working on several things: the eponymous protocol, which they hope will in time replace other ones that don't hide metadata; server software (Magma Classic and Magma Dark); and an email client (Volcano).
Dark Mail functions a bit like Tor. The sender's email server (domain) knows just the recipient’s domain. Once the email arrives on it, the server decrypts the “to:” field and routs the email to the recipient's email account.
The recipient's server knows only the domain from which the email arrived, and the sender's only the domain to which it is sent. If the authorities are passively monitoring internet traffic, they can know only the domains involved, but not the accounts.
Naturally, this can't thwart the authorities efforts if the have access to these domains - usually by obtaining a subpoena - but not all domains keep the data in question.
The project is still ongoing, and the Dark Mail protocol is still being worked on to solve things like hiding the recipient from the sender (and vice versa) if both use the same domain, but Levison hopes that by putting "the base that is Dark Mail in place, people will be able to build more secure alternatives on top of it."
He also shared that he had the idea for and has visualized Dark Mail's concept five years ago, but that, at the time, he didn't think it was needed or that users will clamor for it. Now, of course, the need is there and potential users are willing to pay for a solution.
Reading our newsletter every Monday will keep you up-to-date with security news.
Receive a daily digest of the latest security news.