Since Edward Snowden revealed that the US government is spying on everyone, there has been a boom in the sales of expensive “difficult to hack” phones. Two products new products in the last five weeks show how the market place for off the grid communications is growing.

First one there was the Blackphone, a handset which started shipping on June 30 for $629, and last week there was an app called Signal which appeared last week. Blackphone and Signal use encryption developed by world-class cryptographers and developers who hate the US government.

Signal maker Open Whisper Systems wrote on its blog that in an environment of increasingly pervasive surveillance, it wanted to make it as easy as possible for anyone to be able to organize and communicate securely. Blackphone uses Silent Circle, that allows users to send encrypted voice calls and texts to one another. Silent Circle's software is already available for iPhone and Android phones, but the company says Blackphone uses a sexed up version of Android that makes it harder for hackers to take control of the phone and listen in.

Signal maker reports that the software had 70,000 downloads on the first day, probably because the service is free.