system/secure_communication is a SAP Parameter attribute which is used to control ssl configuration for system internal communication information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
With this parameter you can activate the SSL encryption of the internal
communication of the application server.
Currently only the internal connections to the message server are
encrypted.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.