Slides Here: https://defcon.org/images/defcon-22/dc-22-presentations/Levison-Watt/DEFCON-22-Levison-Watt-Dark-Mail-UPDATED.pdf

Dark Mail
Ladar Levison FOUNDER OF LAVABIT, LLC
Stephen Watt LEAD DEVELOPER, REFERENCE IMPLEMENTATION, DARK MAIL
Data privacy and anonymity have long been cornerstone interests of the computer security world, but not particularly important to the general public. News events in the past year have seen the political climate shift radically, and now data privacy has become big business with secure mail solutions being the focal point of this new found attention.

Dark Mail is not the only solution in the secure mail space, but just as Lavabit’s preoccupation with privacy and user autonomy was a rarity when it started over a decade ago, it hopes once again to push mail security forward into a new frontier. It is Dark Mail's objective to achieve the highest degree of security possible - with the introduction of an interoperable mail protocol as an open standard. To that end, we are publishing documents describing the protocol, along with a reference implementations of the client and server under a free software license.

What most of the secure email systems in the privacy race have prioritized in tandem are ease of use for the masses, and cryptographically secure encryption of message contents between a sender and recipient. Additionally, they tend to place trust for private key management and encryption in the hands of the end user, and not the mail server.

While this would certainly be an improvement over traditional SMTP, it leaves much to be desired. Where do other solutions fall short? Metadata. Dark Mail is designed to minimize the leakage of metadata so that ancillary information like subject lines, recipients, and attachments doesn’t fall into the hands of curious third parties. That means all information about the mail and its contents are completely opaque to everybody but the parties communicating - including the servers handling the messages in transit. Accomplishing these goals wasn’t possible using existing standards, which is why we created a security enhanced flavor of SMTP for mail delivery dubbed DMTP.

What separates dmail from competing secure mail designs is the level of security it affords the user while retaining its simplicity of use. We have automated the key management functions, so complex cryptography operations are handled without user interaction. Of equal importance is the need for an implementation that is open to peer review, security audits, and cryptanalysis. Unlike many commercial solutions, dmail isn’t tethered to a single centralized provider; instead it offers the ability for anybody to host secure mail services. Like today, users will be able to access their mail from anywhere, using a web client with client-side encryption, or a traditional client application on their mobile or desktop device for an even greater degree of security. An open standard will guarantee that users have the freedom to adopt any dmail-compatible client or server implementation of their choosing.

Most attendees of this presentation will be familiar with the curious story of Lavabit's demise. While Lavabit's hosted mail service refused to surrender unfettered access to its users' secrets, this course of action may not be the obvious choice for network administrators placed in similar situations. Most digital surveillance efforts require the service provider to be complicit with the wiretapping requests of law enforcement. Dmail aims to protect messages from surveillance and tampering - whether it be subversive or coerced - by placing that capability beyond the reach of service providers. With dmail the keys belong to the user, and the message decryption occurs on the user’s device. Even so, users can choose how much to trust a service provider - with standardized modes that reside at different points along the security vs usability spectrum.