How do I know if its encrypted?

[Hal]

If you want to not be able to read the files on your storage site, then
why not just try reading them?  Check their entropy to make sure it is
maximal, check that they can't be unzipped, unstuffed, displayed as gif
or jpeg files.  When a new format becomes popular add that to the list.
This is all you can do.

What does this gain you?  I'm not sure.  If someone posts encrypted
Windows 95, then publicizes the location and the key, people will get the
data just as easily as if it were not encrypted.

Hal