Silent Circle's encrypted calling service works across iOS, Android and desktop devices.
Silent Circle, a company known for mobile apps designed to thwart government surveillance, has introduced a fixed price, secrecy-cloaking service that lets customers make and receive encrypted phone calls.
The secure voice-and-data calling plan works on Apple iOS and Android smartphones and, eventually, on Windows Mobile systems, the company said. Callers can reach 79 countries, including New Zealand, Australia, United States, China, Russia, most of Europe and the Americas. Large parts of the Middle East and Africa are not covered.
The service aims to challenge not just traditional phone carriers - who still by and large charge steep roaming fees to international travellers - but also to newer, voice-over-internet services that have sprung up over the past decade.
For while Silent Circle undercuts major competitors' roaming costs in many countries, the service's basic attraction lies in its security features.
"What Silent Circle is offering is an augmented level of security beyond what normal phones can offer," said Ben Wood, a senior analyst with mobile research firm CCS Insight. "It captures the zeitgeist in terms of paranoia by answering the question of what more consumers can do to protect themselves."
The offering looks to appeal to international business travellers working with sensitive information including executives, lawyers and bankers, as well as journalists or activists aiming to fend off prying eyes and unwanted listeners in an age of growing criminal, state-sponsored, corporate espionage and internet-wide privacy threats.
While no one is immune to such snooping, Silent Circle offers users a means of encrypted communications that also disposes of records of all calls, texts, messages or documents on both senders' and receivers' devices. This "burn" feature auto-deletes sent messages and attachments at pre-set times.
"Any drug dealer, terrorist or pimp who thinks this sort of service will insulate them would have to be naïve," Wood said. "Nothing is bullet-proof in that regard."
But some security experts see the software as one of the best commercial options available to individuals, businesses and even government workers, albeit one without absolute guarantees of anonymity or the capacity to withstand targeted surveillance.
"It all depends on what your threat profile is," said the Geneva-based company's chief operations officer, Vic Hyder, a former US Navy SEAL officer. "Most people out there will understand that it's the best security I can have and that's good enough."
Silent Circle was founded by security expert Mike Janke, another former Navy SEAL, along with internet encryption creator Phil Zimmermann and Jon Callas, inventor of Apple's whole disk encryption system.
The new calling plan starts at $US12.95 a month for 100 minutes of outbound calls and runs up to $US39.95 for 1000 minutes, comparable to premium price plans offered by internet communications services such as Microsoft's Skype and Rakuten's Viber - but with greater security.
Customers receive a personal, 10-digit phone number from one of 26 countries that they can use to receive calls when travelling. Calls can be received from anywhere in the world at the calling party's standard long-distance rates.
The plan charges outbound calls that Silent Circle members make to non-Circle members - anyone with a landline phone in the 79 countries covered by the plan and the 42 countries where mobile phone users are reachable.
Outbound calls provide what Hyder calls "a bubble of encryption" that conceals the contents of a call as it is transmitted to Silent Circle servers in Canada and Switzerland, before it is then sent out to public phone networks.
In June, the company also started shipping its first mobile phones. The "Blackphone" comes loaded with a customised version of the Android operating system known as PrivateOS along with a suite of security and privacy apps from Silent Circle.
Hyder said KPN in the Netherlands and Telcel in Mexico, a unit of Carlos Slim's America Movil, were in the early stages of testing the phones for possible mass market retail sales starting later this year or early in 2015.