ECM EMM
(1) Entitlement Control Message
(2) Entitlement Management Message
ECM
(a) It consist of CW Control Word which is content Encryption Key.
(b) It also consist of Content_ID.
(c) Description of the rights required to access content.
Note:- ECM is ciphered using Broadcast Key.
EMM
It consist of ,
(a) Subscriber-ID
(b) Rights Update
(c) Key Update
Note: The EMM is ciphered using a Management Key
Now lets have a idea of Broadcast key and Management Key,
Broadcast Key
This key is comman to all subscribers of a given service to service provider.The Broadcast key frequently change by means of EMM.
A service provider can spend evey month EMMs to update Broadcast key and users entitlements.
So in case of compromised Broadcast Key, EMM message would be sent to all the users to update the broadcast key.
Management Key
EMMs are used to convey rights or invalidiate the users.
The EMM are encrypted with a Management key belonging to the service provider.The EMM message can only read by Smart Card, which stores the Management Key.
The service provider may associate with one Management Key to a single user or a group of users..Group of users may be easily handled by defining a Key hierarchy for the Management Key.
It is also possible to have a mechanism on the Smart Card allowing the updae/remove/add of a service provider’s Management Key.
