Thanks for reminding me about that half of my intended reply, Martin- You encrypt files to keep people from looking at them. Medical facilities aren't going to have the resources, time, money, skill or interest to beother to crack you data. And even if you tell them to look, if they don't have the key, it's gibberish.

If you want them to be understood by any computer, plain, basic TXT files are best, even after 20 years, with PDF and basic HTML with JPGs and GIFs your next options if you feel that you really, really need to have photos.