According to E. Snowden Signal is secured even if used by Patriots. It can be understood since there is no central server (like Whatsapp of FB messenger) for saving text. I use signal and copies of my text are only on my devices. You can even set a timer and messages will disappear thereafter (like Mission Impossible :-). However if you want better confidentiality you can used apps like encrypto to cipher any kind of files with a shared Key.

I know you have been told differently and many people think that way but Snowden is not a hero. He is a turncoat who got hundreds of agents killed, one was a personal friend. He used the release of information as a cover to steal something very valuable and use it against America. If you know what @jack is to Obama than you know what I am referring to. Edward Snowden needs to be hung by his neck until dead. He will never be pardoned and if he ever does see America again it will be in shackles until he is put to death.