Fix iv parameter description
@@ -277,7 +277,7 @@ Parameter Type Description
========= ================ =====================================================
url string **Required.** The URL to the file.
key JWK **Required.** A `JSON Web Key`_ object.
-iv string **Required.** The Initialisation Vector used by
+iv string **Required.** The 128-bit unique counter block used by
AES-CTR, encoded as unpadded base64.
hashes {string: string} **Required.** A map from an algorithm name to a hash
of the ciphertext, encoded as unpadded base64. Clients
