I have a Mac OS X and a flash drive and I would like to store some files as a backup to carry with me in case I completely lose access to my computer (e.g. theft). I would like to encrypt these files. I know close to nothing about how encryption works. It is possible I will need access to these files on another system, OS X or Windows, etc.
How do I encrypt them on one machine so that another one will understand how to decrypt them? (of course, given that I remember the password I used to encrypt them).
I have found solutions like FileVault native to OS X (but I don't know if it will decrypt on another machine) and GPG (which I did not understand that well), I tried using AESCrypt (but it only encrypts file-by-file or a zip archive, which is awkward), I've read that TrueCrypt has been discontinued, etc. What are my options?