Added os-brick adjustments in the Image Encryption spec

A description for the changes in os-brick is added to this spec.

Change-Id: Icc5a393b6ed5ab162d2456531500de0508949251
Co-Authored-By: Markus Hentsch <markus.hentsch@secustack.com>

specs/train/image-encryption.rst

@@ -140,6 +140,15 @@ used to encrypt an image, we will let Glance register as a consumer of that
 key (secret in Barbican [1]) when the corresponding encrypted image is
 uploaded and unregister as a consumer when the image is deleted in Glance.
 
+The methods for encryption and decryption of files - in this case images -
+will be written in a driver like manner in os-brick so the image encryption
+can be extended with another encryption format easily. The encryption driver
+should focus a specific encryption format and implement exactly one encrypt
+and one decrypt method, both based on a cipher implementation of GPG aes.
+This driver may be simple wrappers around an existing implementation. An
+abstract base class should be defined and be used for the implementation of
+GPG encryption (and might be used for other implementations in the future).
+
 
 Alternatives
 ------------
@@ -240,7 +249,7 @@ Other deployer impact
 Developer impact
 ----------------
 
-* To use the encoding and decoding of images in the library, we need to
+* To use the encoding and decoding of images in os-brick, we need to
   execute priviledged functions. We decided to use privsep for this as in
   nova.
 
@@ -274,6 +283,8 @@ Work Items
   creating encrypted images from volumes using the proposed image encryption
   format (GPG)
 
+* Add encryption and decryption methods for the GPG format in os-brick
+
 
 Dependencies
 ============
@@ -328,5 +339,5 @@ History
 
    * - Release Name
      - Description
-   * - Stein
+   * - Train
      - Introduced