How does CMTS MIC work- what is md5'd?

[megadork]

Can someone please point me to documentation on what is md5'd in the CMTS MIC? I am trying to understand specifically how DOCSIS 3 security model would prevent a user from getting a legitimate subbed config for one tier and then changing to a different (cheaper) tier and continuing to use the previous config. I'm very much enjoying learning about how DOCSIS 3 security feature work and would love to read some documentation on how these are implemented on the CMTS.

Thanks in advance!