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!

[drewmerc]

this image sums up md5



http://en.wikipedia.org/wiki/MD5

[neo_]

Open your config file in a hex editor, the MD5 MIC hash is always between "07 10" and "FF" towards the bottom.

[megadork]

Open your config file in a hex editor, the MD5 MIC hash is always between "07 10" and "FF" towards the bottom.

Thanks for your replies gentlemen.

Is there any system in place that tries to prevent the modem from simply saying "here's how I'm configured, exactly as you told me CMTS" and then proceeding to configure itself differently using a config file stored locally? I'm new to this scene and just trying to understand the security model a bit better as it relates to CMs modifying / using a config other than intended.

Thanks again.

[daviddds]

Yes, there is a system in place for that.. the CMTS tells the cable modem when it can talk upstraem, and how much it can talk at a time upstream, if it tries to talk more than its allowed, the CMTS will boot it off the network, same for downstream, the CMTS will only send data as fast as the QoS classifier the modem is registered with.