There are two messages in the dynamics protocol. Delta messages are used to send deltas to other endpoints in a shared space. Delta Ack messages are used to acknowledge the receipt of deltas.
Dynamics messages consist of a wrapper in a format similar to MIME, as described in [RFC2045]. This wraps the compressed, secured payload. This is an encoding, using a subset of WBXML, as described in [WBXML1.2], of the secure XML, as described in [XML10].
The secure XML uses XML namespaces, as described in [XMLNS], and contains the message contents. These contents are encrypted using the AES algorithm, as described in [FIPS197] in CTR mode, as described in [BCMO800-38A], with a per-space symmetric key. Encryption prevents anyone who is not a member of the shared space from reading the message. The message contents are also signed using the ESIGN algorithm, as described in [IEEE1363a]. The signature private key is unique for a single space and a single member. Signing is used to guarantee both message integrity and message authenticity.
Once the secure XML has been decrypted, the structure and attributes of the decrypted XML determine how dynamics processes the Delta or Delta Ack message.