[Cryptography] Does this keying scheme make sense?

[Jason Richards]

John Levine:
> I was talking to a guy at a conference who sells a package which,
> among other things, encrypts files in cloud storage with each file
> having a different key.  The keys are all generated from a secret
> keystore seed in a way that is supposed to be secure.

There's quite a few pieces of software out there with this
functionality. Some of the better ransomware works in this way.

J