Warren, thank you very much indeed for this information. I was not aware of GnuPG, so thanks for correcting me on this. Having followed the links you provided, GnuPG does seem to do everything you state. However, when I started to read the GnuPG documentation, my eyes started to glaze over! I am not technically confident at all in this area, and I know that I do not have the skills, knowledge or confidence to correctly implement what is required; and also to have certainty that I’ve implemented things correctly.
What is most important to me is robust encryption (i.e. AES256), ease of use and open-source verification. And also cross-platform functionality between Windows and OS X, which Svante has confirmed is currently under development. This is so important for someone like me who does not fully understand the complexities of encryption, and does not have the knowledge or confidence to know when/if I’ve implemented the program correctly. All I need is fast, simple encryption of key files and folders.
So I very much agree with the points you have made. But I also strongly agree with the points made by Svante in terms of simplicity and ease of use.