Silent Circle is a relatively new and well-reviewed service for providing encrypted voice communications domestically. In the wake of the Prism scandal and "massive demand," the company announced that it's dropped the price of its annual subscription package for four services: encrypted mobile calls, encrypted text messaging, encrypted VoIP audio and video calls, and encrypted email. The company says it's been independently audited to ensure there are no backdoors for eavesdropping on service users.
One caveat with the service, however, is that for communications to remain fully encrypted in transit, they must be made between two Silent Circle subscribers. Still, that might appeal to businesses or activists worried about their communications being intercepted, or the identity of people they're speaking with tracked.
4. Redphone, For Secure Android Calls, Texts.
Android users, meanwhile, can get secure voice calls and texts via open source software from WhisperSystems. Redphone enables encrypted calling between two devices that use the software. TextSecure encrypts texts. Both applications have been audited to ensure they don't contain backdoors. As with Silent Circle, one caveat is that people on both sides of the conversation must be using the software.
5. PGP, For Data Encryption.
What else is possible? PGP -- or its open source equivalent GPG -- can be used to encrypt data and emails, but many people find it difficult to use. Notably, Snowden had to send a homemade video to Greenwald, showing him how to set it up.
6. Power Down Your Phone.
Mobile phone users can pull a Jason Bourne and remove the battery from their cell phone when they're not using it, thus preventing the device from pinging cell towers and revealing their approximate location. But as soon as you put the battery back in, you'll be trackable again, because the network has to reach your phone to provide voice and data services.
As Christopher Soghoian, principal technologist and senior policy analyst for the ACLU's Speech, Privacy and Technology Project, told the Post, "The laws of physics will not let you hide your location from the phone company."
7. Expect Metadata To Be Captured.
For any unencrypted call made using your cellphone, the metadata can be -- and probably is being -- intercepted. From an intelligence standpoint, metadata is a goldmine: one Nature study suggests that by cross-referencing "human mobility" metadata, only four location points -- involving location and time -- are required to uniquely identify someone 95% of the time.
In other words, there's no way to use a mobile phone and avoid metadata capture.
The services detailed above, however, will at least encrypt your communications, avoiding capture via programs such as Prism. That said, they carry usability caveats, as well as integrity worries: what if the NSA's cryptographic capabilities already allow it to successfully defeat those services, or it's found an exploitable vulnerability that accomplishes the same result?
Then again, if you think about these things too much, you might want to join the tinfoil hat crowd. At a certain point, anyone who opts for encrypted communications will have to trust in the available, audited tools.