Hey all,
   Am mulling over a federated datastore for zero-knowledge web
   applications, using hashcash as a "commitment" price for otherwise
   gratis data storage. All very straightforward, but:
   Zero knowledge is as much for host protection as client protection.
   Hosts don't WANT plaintext.
   Short of stupidly CPU-intensive stuff like letter counting, UTF8
   decoding, etc, how might a server verify it's receiving encrypted data?
   I was thinking a function that estimates apparent entropy and rejects
   anything that doesn't look random enough to be encrypted, what such
   functions are available, fast, widely implemented?
   --
   Sent from my Android device with K-9 Mail. Please excuse my brevity.