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Vineet Arora · Guest

I am putting down our requirements. Please find out if you can get
answers for them

Module Requirement :- We are developing solution which sells DRM
protected audio files. For DRM protection we are planning to use MS
DRM. We are planning to provide following functionality to the user
using MSDRM

1. Issue split license

Scenario :- Let us say a total license that we can provide each user
for one audio file is "Allow play on 3 computers, 10 CD burn count ,
unlimited SDMI transfers". Here we want to give him a chunk of 10 CD
burn count on each computer. e.g. on Computer 1 he takes 3 cd burn
count , on computer2 4 CD burn count .... To implement this we are
issueing separate license on each machine and we are disabling the
backup/restore for the license.

Questions :- (i) Is their a better way to solve the same problem?
(ii) does this provides a hole which end user can
exploit ?

2. Authorize/Deauthorize device

Scenario :- User has bought songs on computer1 and for some reason
user needs to sell this computer and he wants to transfer all the
songs from computer1 to computer2 . We want to provide the user
flexibility where user choose to surrender his licenses from computer
1 and ask for re issue on computer 2. We have come up with two
solution to solve the problem. We have tried the first one but we have
not tried the second solution till now.

Solution 1 :- User selects the songs which he wants to deauthorize, we
call a method in "Windows Media Format SDK 9 Series" to get the
license state on current machine. Then we request the server to back
up this information. After that we issue a high priority license with
0 Play , 0 CD burn count which is equal to null license. Then on
Computer 2 we issue a new license using rights stored in our database
when we revoked the license from computer 1.

Solution 2:- Issue each song with a unique key for the device id and
song id combination . When user requests for deauthorize we call
IDRMRights->GenerateContentRevocation using the unique key for each
song selected by user.

Till now we are planning to use only solution 1 , we have not tried
solution 2
Questions:- (i) Is their a better way then solution 1 / Solution2 to
solve the same problem ?
(ii) does this provides a hole which end user can
exploit ?
(iii) will solution 2 work ? If it works what is the
implication of this on performance ?

3. Reading license information

Scenario :- User has bought songs and we need to show the license
usage status for all the songs selected by user.

Solution :- Ask user to specify the path of the song file and using
"Windows Media Format SDK 9 Series" read the license information and
show it to user

Issue :- We do not like this solution where user needs to select the
song. we want to go through the folder which has all the .lic files.
We know that this folder is fixed and we can get the path of the
folder from registry. We want to detect the lic files associated
with song ids which we have sold and read the license usage
information.

Questions:-
1. Is it possible to find the .lic file using a song id ?
2. Is it possible to read the .lic file using "Windows Media Format
SDK 9 Series" ?

Thanks
-vineet

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