Comment Keys in the box... (Score 2) 434
Instead of storing data in the box directly, where you then rely on media retaining viability over 25 years you could always strongly encrypt the data you would like to logically store in the box and then write (or etch in stone, whatever) the decryption key and store that human readable quantity of data in the box and then maintain the cipher-text outside the box in a redundant distributed fashion over multiple generations of media. Of course I fail to see what the advantage of keeping the data secret over the time period would obtain, and it prevents transcoding to new file formats, so I'd just suggest keeping copies of the data as you would any data you want to have in 25 years (not locked in a box).
You see, physical objects are placed into a time capsule because they would normally deteriorate and not be archived properly if they weren't removed from the harsh existence of everyday life. Data however doesn't work like that, neglect is the biggest problem and hence a time capsule is not a good means of preserving data the way it is for preserving objects.