Key specs

--- Server specification ---

INCOMING MESSAGE
	POST <url>
	<payload>

		if url="/key": payload is a 32 byte octet stream (AES256 key)
		if url="/id": payload is a 64 byte octet stream (SHA512 hash)


OUTGOING MESSAGE
	<status>
	<payload>

		if status=200|201:
			if url="/key": payload is a 64 byte octet stream (SHA512 hash)
			if url="/id": payload is a 32 byte octet stream (AES256 key)

	Possible error status codes:
		400 Bad Request
		401 Unauthorized
		402 Payment Required
		406 Not Acceptable
		429 Too Many Requests
		500 Internal Server Error



CRYPTO PATH
	/key:
		AES256-key  ->  SHA512-keyhash    =>    obj.id		(obj: item of the JSON store)
    "  "     ->    AES256-enckey    =>    obj.key
  	passphrase -^                      (passphrase given as stdin)

	/id:
		SHA512-id ->  [compare to keyhash]
      obj.key   =>  AES256-enckey ->  AES256-key  ->  SHA512-keyhash
      ....... passphrase -^
		[if keyhash =/= id: passphrase wrong, unauthorized!]
		[else: return payment status]

Note: To use the passphrase as AES256 key, it has to be 32 bytes large.
	E.g. make a SHA256 hash from the stdin

---