I have tried a few encryption and digital signature tools in the past. Each and everyone of them have found the same fate: abandonware. Not too long ago there was miniLock. Gone. Then came Keys—oh, so nice! Gone.
The only one that hasn’t let me down, and the reason why I will no longer look for another tool, is GnuPG, a free implementation of the OpenPGP standard. Regardless of the flaws some might find in it, it works quite well, and I am sure it will continue to for the foreseable future.