3.1.5.2.2.6 LogonAcceleratorToken

This parameter MUST be Base64-encoded [RFC4648] data used by the STS to cache information about the user as a [RFC2965] cookie. The protocol does not constrain the format of this data since it is written by the STS for later processing by the STS. STS implementations can use any appropriate data format, and proxy implementations need only write the data to the web browser requestor as an [RFC2965] cookie.