storage used by files

NTFSD
1

hi,

i am writing an encryption filter driver.

if my driver reads from the file system, encrypts the data and writes it
back, will the file system write the data back to the same physical location
or otherwise?

Ho Mun Chuen
@@ “Not everything that counts can be counted;
<” )~ and not everything that can be counted counts"
//\ … Albert Einstein

2

Hi,

Assuming only FAT and NTFS, and that you are not encrypting compressed
NTFS files, yes. Otherwise, no.

Regards, Dejan.

Ho Mun Chuen wrote:

hi,

i am writing an encryption filter driver.

if my driver reads from the file system, encrypts the data and writes it
back, will the file system write the data back to the same physical location
or otherwise?

Ho Mun Chuen
@@ “Not everything that counts can be counted;
<” )~ and not everything that can be counted counts"
//\ … Albert Einstein

You are currently subscribed to ntfsd as: xxxxx@alfasp.com
To unsubscribe send a blank email to xxxxx@lists.osr.com

–
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.

3

Also throw in the assumption that no other file system filter is on the
stack doing something interesting. Since any assumption on the
possibility of other filters is a bad idea (someone will always do it
and your code is then wrong), you should never assume this will
work.

Don Burn
Egenera, Inc

----- Original Message -----
From: “Dejan Maksimovic”
To: “File Systems Developers”
Sent: Tuesday, December 31, 2002 8:04 AM
Subject: [ntfsd] Re: storage used by files

>
> Hi,
>
> Assuming only FAT and NTFS, and that you are not encrypting
compressed
> NTFS files, yes. Otherwise, no.
>
> Regards, Dejan.
>
> Ho Mun Chuen wrote:
>
> > hi,
> >
> > i am writing an encryption filter driver.
> >
> > if my driver reads from the file system, encrypts the data and writes it
> > back, will the file system write the data back to the same physical
location
> > or otherwise?
> >
> > Ho Mun Chuen
> > @@ “Not everything that counts can be counted;
> > <” )~ and not everything that can be counted counts"
> > //\ … Albert Einstein
> >
> > —
> > You are currently subscribed to ntfsd as: xxxxx@alfasp.com
> > To unsubscribe send a blank email to xxxxx@lists.osr.com
>
> –
> 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@acm.org
> To unsubscribe send a blank email to xxxxx@lists.osr.com

4

Maybe. No guarantees.

----- Original Message -----
From: “Ho Mun Chuen”
To: “File Systems Developers”
Sent: Monday, December 30, 2002 10:39 PM
Subject: [ntfsd] storage used by files

> hi,
>
> i am writing an encryption filter driver.
>
> if my driver reads from the file system, encrypts the data and writes it
> back, will the file system write the data back to the same physical
location
> or otherwise?
>
> Ho Mun Chuen
> @@ “Not everything that counts can be counted;
> <” )~ and not everything that can be counted counts"
> //\ … Albert Einstein

5

Usual file systems - yes, but conceptually there are log-structured FS
which do all new write to a new block. No LFSs are shipped with NT,
they are used in SAN/NAS boxes.

Max

----- Original Message -----
From: “Ho Mun Chuen”
To: “File Systems Developers”
Sent: Tuesday, December 31, 2002 6:39 AM
Subject: [ntfsd] storage used by files

> hi,
>
> i am writing an encryption filter driver.
>
> if my driver reads from the file system, encrypts the data and
writes it
> back, will the file system write the data back to the same physical
location
> or otherwise?
>
> Ho Mun Chuen
> @@ “Not everything that counts can be counted;
> <” )~ and not everything that can be counted counts"
> //\ … Albert Einstein
>
>
>
>
> —
> You are currently subscribed to ntfsd as: xxxxx@storagecraft.com
> To unsubscribe send a blank email to xxxxx@lists.osr.com
>

6

thanks for the info. how about RDR to FAT or NTFS on the remote machine?

Ho Mun Chuen
@@ “Not everything that counts can be counted;
<” )~ and not everything that can be counted counts"
//\ … Albert Einstein
----- Original Message -----
From: “Dejan Maksimovic”
To: “File Systems Developers”
Sent: Tuesday, December 31, 2002 9:04 PM
Subject: [ntfsd] Re: storage used by files

Hi,

Assuming only FAT and NTFS, and that you are not encrypting
compressed
NTFS files, yes. Otherwise, no.

Regards, Dejan.

Ho Mun Chuen wrote:

> hi,
>
> i am writing an encryption filter driver.
>
> if my driver reads from the file system, encrypts the data and writes it
> back, will the file system write the data back to the same physical
location
> or otherwise?
>
> Ho Mun Chuen
> @@ “Not everything that counts can be counted;
> <” )~ and not everything that can be counted counts"
> //\ … Albert Einstein
>
> —
> You are currently subscribed to ntfsd as: xxxxx@alfasp.com
> To unsubscribe send a blank email to xxxxx@lists.osr.com

–
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@pmail.ntu.edu.sg
To unsubscribe send a blank email to xxxxx@lists.osr.com

7

No.

Ho Mun Chuen wrote:

thanks for the info. how about RDR to FAT or NTFS on the remote machine?

–
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.

8

thanks. is there anywhere that this is documented?

Ho Mun Chuen
(Office) 63733409 (Pager) 93253507
@@ “Not everything that counts can be counted;
<” )~ and not everything that can be counted counts"
//\ … Albert Einstein
----- Original Message -----
From: “Dejan Maksimovic”
To: “File Systems Developers”
Sent: Friday, January 03, 2003 9:56 PM
Subject: [ntfsd] Re: storage used by files

No.

Ho Mun Chuen wrote:

> thanks for the info. how about RDR to FAT or NTFS on the remote machine?

–
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@pmail.ntu.edu.sg
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