The makers of a smartphone launching next month claim it offers complete security from snooping on all forms of communication. But full details of the Blackphone and how it maintains privacy haven’t yet been published.

The Blackphone is a joint project of Geeksphone, a Spanish smartphone manufacturer, and Silent Circle, a US firm which already offers encrypted communications as a paid mobile device service. Phil Zimmerman, the man behind the Pretty Good Privacy encryption system for secure e-mail, co-founded Silent Circle.

The phone will run a modified version of Android known as PrivatOS. The hardware specs haven’t been published yet, other than a suggestion that the handset will be “high end.” PrivatOS will eventually be published as open source code.

Blackphone will be carrier-independent and should work on any GSM-based network. Pricing is not yet confirmed, though there’s a suggestion it will be cheaper than the likes of the iPhone 5S and Galaxy S4. Of course, it’s unlikely you’ll be able to get it with a subsidy from the major carriers, so chances are you are looking in the mid-hundreds of dollars. There’s no mention of any ongoing service charges for the privacy features beyond the handset purchase cost.

It looks as if different forms of communication will be protected in different ways. Web browsing will be through a virtual private network, while e-mails will be encrypted.

The existing Silent Circle service for voice and video calls uses a Voice Over Internet Protocol system with encrypted data. That means it’s very possible the privacy protection will only work if you phone other users of the handset or people running the Silent Circle software on their own device.

Silent Circle chief Mike Janke says the business behind Blackphone will be based in Switzerland, a country which is not exactly know for its cooperation with international law enforcement requests. Payment processing will be carried out by an independent firm and the only details Blackphone itself will have about each customer is a username and a phone number.

Janke says 30 businesses have already agreed in principle to buy the handset in bulk. He also claims the US State Department asked to buy the phone, but was turned down.

The phone will get an official unveiling at the Mobile World Congress event in Barcelona next month, at which point pre-orders will be accepted.