Only works over VoIP. I wonder if you could do analog audio encryption over the standard cell network.
No, audio codecs will destroy encrypted data. It makes more sense to do encrypted voice over circuit-switched data (e.g. Voylent), but I don't know if the carriers even support CSD any more.
They sell third party encryption devices that connect to cell phones, encrypt outgoing voice and decrypt incoming voice.
I've wanted to make this for a long time, but accepted that I didn't (and don't) know enough about security to do it right. I hope this proves to be a secure implementation. Looking forward to a security review by someone who knows a lot more than I do.
Yes this is awesome! I have no need for an app like this but I've still always thought it would be a great idea.