Is it even possible on android? Is there a FOSS dialer to optionally encrypt some phone calls (non voip) using a pre-shared key with other party?
Is it even possible on android? Is there a FOSS dialer to optionally encrypt some phone calls (non voip) using a pre-shared key with other party?
I think this is not doable. You don’t have access to the voice codec to start with, and the phone at the other end generally won’t receive the bit stream coming out of it anyway. With a non-rooted phone it’s hard to even get to the voice stream. You might be able to send subliminal encrypted text messages through a voice channel and that could be kind of cool, and hard to detect. That idea has been around for a while but I don’t know of existing software that does it.
With VOIP, of course there are many encrypted systems available.
Added: also I assumed throughout that you meant present day mobile phones. With land phones at both ends, it may still be doable using dialup modems, but that was a 1990s thing and was pretty awful when you got down to it. It existed though.