Smartphones as of now are insecure. This is not necessary. A big smartphone revolution comes with the upcoming Librem phone because it has LTE, hardware switches and was built with the purpose of open source. More like it will most probably follow, Ubuntu Phone, Sailfish, Wayland stabilizing and KDE Mobile are pointing in that direction.
While waiting the only pseudo-secure phones (for non-super serious activities and having relative user-autonomy and "security") are the ones recommended by the GNU Replicant project (
https://replicant.us/). OS-wise Lineage-MicroG or Replicant are the best as of now, Replicant is just way harder to find a suitable hardware-software match for, since it's a GNU-terms free software OS and thus contains no binary blobs (required for most smartphone comms, except GSM). E2E encrypted comms, anonymous overlay networks and P2P programs need to be integrated way better with mobile OS until a serious, newb-proof approach to this is realistic and capable of emerging a technically enlightened counter-culture/society/economy. It's theoretically feasible, just not anywhere in sight just yet. It seems as if though the material conditions just aren't up to task; no surprise considering we're still in the x86 INTEL/amd duopoly.
Also never expect others to have secure phones. If you plan on using tech for some controversial end then plan that out beforehand with new hardware, software.
TL;DR: hardware: Replicant recommended smartphones; software: Google-free Lineage-MicroG w/ Copperhead's 'Noise' fork of Signal that updates through F-Droid, as opposed to OWS' Signal.
>>2762>BitmessageCompromised:
https://en.wikipedia.org/wiki/Bitmessage#Security