Your encryption routines are too slow. MediaPlayer must be able to read the data quickly enough to keep up.
----- Original Message -----
From: biswaroop
To: File Systems Developers
Sent: Wednesday, April 02, 2003 4:31 AM
Subject: [ntfsd] Re: CDFS driver doubt help please
Hi Everyone,
Yeah, you are right David.
My software has a filter driver which does the decryption
taking the passwd as the key. If it is right then the data
becomes readable otherwise junk.
The second method ( of marking any of the descriptor fileds
in the Filesystem in which its written(eg. ISO 9660) can
be used and on validating that we can decrypt using a
fixed key(embedded in the filter driver).
I have a problem. for (txt and doc files ) its working properly
but for mpeg files(on the fly decrypting) i am not able to
play it from the MediaPlayer directly but if i copy it to the local disk and then play it works.
Is that the Windows Media player has some time out
concept while trying to decompress and play a stream
containing mpeg format data??
Thanks anyway.
Biswaroop
----- Original Message -----
From: David J. Craig
To: File Systems Developers
Sent: Tuesday, April 01, 2003 1:07 AM
Subject: [ntfsd] Re: CDFS driver doubt help please
The data is probably not actually encrypted on the CD if, as you state, you are using the standard device drivers in the stack. You didn’t mention any filters or any other kernel mode component that is unique to your software. If there is a filter actually doing the decryption then see the next paragraph.
A file system filter that works properly with the MS supplied filesystem will place all data in the cache as plaintext. If a second open for a file occurs before the cache is invalidated, the plaintext data is present and will work. Your filter must invalidate the cache during cleanup (or maybe close) so you can go to the media again. Another option is to have something on the CD that will be validated with the entered password and will tell the filter that access is permitted if the validation works.
----- Original Message -----
From: biswaroop
To: File Systems Developers
Sent: Friday, March 28, 2003 4:27 AM
Subject: [ntfsd] CDFS driver doubt help please
Hi Everyone,
I have a media(CD) written in a Encrypted form.
When i insert the media, a exe is executed and asks
the user for the password.
Upon getting the password i use this as a key to decrypt
the data i get from the cd(using default CDFS driver)
and the data is shown .
But after i eject the CD and put it again inside the CD drive
the exe is executed and asks for the password but now
i give a wrong password still i am able to view the data
on the media rightly.
I have doubt, as far as i know CDFS driver implementation
tries to find new volume is there or not by calcluating some
magic no from the volume data and next time if it encounters a new volume it recalculates the magic no
and matches with the stored one for the previously mounted
volume.
Hence in my case , as i believe both the time the volume’
was same hence the second time when i inserted the
media even though giving a wrong password made read the
volume because the CDFS driver was using its previously
maintained volume structure rather than creating a new
one …and hence my security cover of password is
broken??
Can anybdoy guide me if my understanding is
right for the problem or any solutions to handle
the problem??
Thanking you in advance and waiting for help.
Bye
Biswaroop
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