Which smartphone to choose for corporate communication?

Question

Encryption

There is a task to collect (install OS, applications) a number of phones for "paranoids":
Plan:
- take a smartphone (question 1 - maybe someone knows the best option)
- install cyanogenmod Android on it, and programs from https://prism-break. org
- use a p2p messenger with encryption and the same dialers to communicate -
Use VPN
Tell me in a nutshell:
"places?
2) What are the most secure open source communication applications you know?
3) Which device to choose?
We do not consider phones with an encryption module, they are too expensive.
Please answer without jokes.
I have read many articles on Habré on this topic, but the issue needs to be sorted out urgently, so I am writing the question to you. Thank you.

Answer 1

The headset itself (or the sound of a separate computer: ADC <-> DAC) should provide an audio-voice crypto-channel. Preferably with 2/3 factor semi-automatic authentication.
Smartphone - well, to play it was possible. (it doesn't matter - protection 0)

Answer 2

Basically a BlackBerry.
But you need a feint: buy phones "there", register and bind them too "there". Services to use at the place of residence. This is legal (as long as the phone is not intended to discuss illegal transactions, transmit protected data, or serve government clients).
Why is everything "there"? Well, because here (I'm talking about the Russian Federation) it's somehow strange with them. The profile office obliges to push the equipment in (conditionally) the server. The idea is to have access. And the hairy hand of a competitor, IMHO, may well give ... Well, let's say, 10 thousand euros to a familiar retired general, who in his own way can merge everything. Everything is strictly IMHO, for 10 euros and a system administrator it would be possible to bribe just the head of the department.
Well, another option...
Phones are for data use only. Drive the voice over SIP, there are now, like, already two protected transport options. Messages - this good dofigischa.
I don’t really believe that a competitor will hack into these devices through vulnerabilities in the OS or will act at the level of the OPSOS (in theory, they can remove the remote voice from the device directly).