Messages are the top-level Structures exchanged between a Client and Server. A Message sent from a Client to a Server is a Request. A Message sent back to a Client from the Server is a Response.

Sending the same Message multiple times (i.e. calling Read ServerState over and over) increases the attack surface. To reduce the attack surface, any Messages can include random data inserted into the AdditionalHeader field of the RequestHeader or ResponseHeader. The key name for this random data is specified in Table 14.

Table 14 – Padding AdditionalHeader Key Name

Name	DataType	Description
Padding	ByteString	Provides random padding that varies the sizes of Messages. The length is random number of bytes from 0 to 128. The value should be a sequence random bytes that are used for exactly one Message.

The Padding should only be used over SecureChannels with a SecurityMode of SignAndEncrypt. The content of the Padding is ignored.