Hi all,
I wrote a FSFD for on the fly encryption and it works fine for both local
and network files. My filter adds some data to the end of each encrypted
file with some neccessary information.
I’m having trouble with encrypting NTFS compressed files - although my
driver gets the paging write operations and encrypts them, it seems that
the actual data written to disk is different than the one I pass to the
next driver.
I’m also having trouble encrypting files on the network that are marked as
available offline, and also encrypting the local cache of these files
(under the winnt\CSC folder)
Any ideas ?
Rami
I believe both compressed files and offline cache have the same base
problem - you just can’t encrypt them correctly:-(
I tried to track this but was unable to - so I decided just to disable
compression on files that I need to encrypt. Since files are rarely compressed
any more (except for the cache in the WinNT folder, which will HARDLY be
encrypted by anyone), I think this is good enough.
I found several implementations of an encryption driver on the net, and
all of them either disable compression for encrypted files - or just work with
a flaw:-)
Deja.
xxxxx@aliroo.com wrote:
Hi all,
I wrote a FSFD for on the fly encryption and it works fine for both local
and network files. My filter adds some data to the end of each encrypted
file with some neccessary information.
I’m having trouble with encrypting NTFS compressed files - although my
driver gets the paging write operations and encrypts them, it seems that
the actual data written to disk is different than the one I pass to the
next driver.
I’m also having trouble encrypting files on the network that are marked as
available offline, and also encrypting the local cache of these files
(under the winnt\CSC folder)
Any ideas ?
Rami
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–
Kind regards, Dejan M. www.alfasp.com
E-mail: xxxxx@alfasp.com ICQ#: 56570367
Alfa File Monitor - File monitoring library for Win32 developers.
Alfa File Protector - File protection and hiding library for Win32 developers.
Dejan,
you wrote on Monday, September 23, 2002, 12:17:27:
DM> I believe both compressed files and offline cache have the same base
DM> problem - you just can’t encrypt them correctly:-(
Even Microsoft’s own EFS doesn’t do it. Try to tick both the Encrypt and
Compress check mark in a file’s advanced properties…
Ralf.
Yep, that should be good enough not to try it:-) Thanks for reminding me
of that.
Ralf Buschmann wrote:
DM> I believe both compressed files and offline cache have the same base
DM> problem - you just can’t encrypt them correctly:-(Even Microsoft’s own EFS doesn’t do it. Try to tick both the Encrypt and
Compress check mark in a file’s advanced properties…
–
Kind regards, Dejan M. www.alfasp.com
E-mail: xxxxx@alfasp.com ICQ#: 56570367
Alfa File Monitor - File monitoring library for Win32 developers.
Alfa File Protector - File protection and hiding library for Win32
developers.
I was able to get my filter working correctly with EFS, but not with
compression. NTFS compression appears to play some strange games with
the cache… Often it seems to skip the paging I/O path entirely, and
other times I get all 0’s when performing a hand-rolled paging I/O read
on a portion of the file I know contains data (and the same read
performed shortly afterward will return the correct data).
Remember you can always decompress any file you wish by sending down the
FSCTL_SET_COMPRESSION yourself (and prevent further attempts to compress
by eating any FSCTL_SET_COMPRESSION that your filter intercepts).
- Nicholas Ryan
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Dejan Maksimovic
Sent: Monday, September 23, 2002 3:17 AM
To: File Systems Developers
Subject: [ntfsd] Re: Encryption FSFD and NTFS
compression/Offline foldersI believe both compressed files and offline cache have
the same base problem - you just can’t encrypt them correctly:-(
I tried to track this but was unable to - so I decided
just to disable compression on files that I need to encrypt.
Since files are rarely compressed any more (except for the
cache in the WinNT folder, which will HARDLY be encrypted by
anyone), I think this is good enough.
I found several implementations of an encryption driver
on the net, and all of them either disable compression for
encrypted files - or just work with a flaw:-)Deja.
xxxxx@aliroo.com wrote:
> Hi all,
> I wrote a FSFD for on the fly encryption and it works fine for both
> local and network files. My filter adds some data to the
end of each
> encrypted file with some neccessary information. I’m having trouble
> with encrypting NTFS compressed files - although my driver gets the
> paging write operations and encrypts them, it seems that the actual
> data written to disk is different than the one I pass to the next
> driver. I’m also having trouble encrypting files on the
network that
> are marked as available offline, and also encrypting the
local cache
> of these files (under the winnt\CSC folder)
> Any ideas ?
> Rami
>
> —
> You are currently subscribed to ntfsd as: xxxxx@alfasp.com
> To unsubscribe send a blank email to %%email.unsub%%–
Kind regards, Dejan M. www.alfasp.com
E-mail: xxxxx@alfasp.com ICQ#: 56570367
Alfa File Monitor - File monitoring library for Win32
developers. Alfa File Protector - File protection and hiding
library for Win32 developers.
You are currently subscribed to ntfsd as: xxxxx@nryan.com
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