Users of the privacy-focused Silent Circle service will now be able to call non-subscribers around the world while still taking advantage of the encrypted network.

Silent Circle, seen as a private and secure version of Skype, was created in 2011 by amongst others Phil Zimmermann, the creator of the widely used PGP (Pretty Good Privacy) email encryption software.

Silent Circle offers phone, text and email services to its subscribers allowing them to make fully end-to-end encrypted communications through servers which are based in Canada.

Today the company announced it is expanding its reach by allowing customers who sign up to one of its international calling plans to make encrypted phone calls to people in 79 countries around the world even if those people are not Silent Circle subscribers.

"Silent Circle's Out-Circle encrypted international calling plans are a major step forward in bringing private encrypted communications capabilities to all corners of the world. Silent Phone and Silent Text already offer unmatched advantages, but with today's expansion we are giving our members a tremendous increase in cost and flexibility benefits," said Mike Janke, Silent Circle CEO.

Subscribers will be given a unique 10-digit Silent Phone number to allow them complete calls "outside the Circle" to and from non-subscribers in 79 countries around the world - which the company says is "four to five times more than its closest non-secure competitors like Skype and Viber".

End of roaming fees

The rise of software like Silent Circle has rapidly increased in the last 12 months as revelations about government spying on citizens around the world has been laid bare by revelations from Edward Snowden.

Silent Circle believes that not only will this additional feature attract the privacy-conscious customers but the move could also disrupt the traditional mobile phone market by completely eliminating roaming charges.

Vic Hyder, co-founder of Silent Circle said the company was "directly challenging the legacy model of mobile carriers" by offering an alternative to traditional roaming fees which he says was an important issue for enterprise and government customers.

"International fees and roaming charges account for a significant portion of European and Latin American business overhead. Our encrypted international calling service completely eliminates roaming charges while protecting members with the use of Silent Phone."