Comment Re:Paper, and physical equivalents (Score 1) 208
A paper record is good. So is a plaintext file well organized and placed on a USB flash drive. Both can be mailed and locked in a safety deposit box, which is about as secure as you can get. Both require physical access, which means any other encryption or security is more likely to confound your subjects than actually secure your data.
In addition, you could encrypt the plaintext file with a well-known algorithm (you can even specify which one and the parameters) using a very strong password contained in your will, to prevent unwanted disclosure.
You could then apply Base64 encoding to the encrypted plaintext file, and print the result in a large font to enable scanning and OCR to recreate the digital file and decrypt it. This should be reliable enough - I don't think any of these technologies are going to go away any time soon.