add note indicating similarity between key backup format and key exports
also copy description of forwarding_curve25519_key_chain from key exports, since
it's a better description
@@ -861,12 +861,14 @@ The ``session_data`` field in the backups is constructed as follows:
algorithm string Required. The end-to-end message
encryption algorithm that the key is
for. Must be ``m.megolm.v1.aes-sha2``.
+ forwarding_curve25519_key_chain [string] Required. Chain of Curve25519 keys
+ through which this session was
+ forwarded, via
+ `m.forwarded_room_key`_ events.
sender_key string Required. Unpadded base64-encoded
device curve25519 key.
sender_claimed_keys {string: Required. Object containing the
string} identity key for the sending device.
- forwarding_curve25519_key_chain [string] Required. Zero or more curve25519 keys
- for devices who forwarded the session key.
session_key string Required. Unpadded base64-encoded
session key in `session-sharing format
<https://gitlab.matrix.org/matrix-org/olm/blob/master/docs/megolm.md#session-sharing-format>`_.
@@ -961,6 +963,9 @@ described as follows:
session_key string Required. The key for the session.
=============================== =========== ====================================
+This is similar to the format before encryption used for the session keys in
+`Server-side key backups`_ but adds the ``room_id`` and ``session_id`` fields.
+
Example:
.. code:: json
