FS Filter to Crypt and Fast I/O

NTFSD
1

Hi all,

I’m writing a FS Filter to encrypt/decrypt files in from a folder in real
time. I did start it with SFILTER sample from DDK IFS. I’m filtering
IRP->Flags with IRP_NOCACHE to encrypt/decrypt buffer. Thus, the cache will
be decrypted rigth? Can I leave Fast I/O unmodified?

Thanks in advance.
Fernando Roberto da Silva.

2

Yes, you need to leave Fast IO unmodified. Fast IO is only used to copy user data to the cache, it is not used to write data directly to disk.

Alexei.
“Fernando Roberto da Silva” wrote in message news:xxxxx@ntfsd…
Hi all,

I’m writing a FS Filter to encrypt/decrypt files in from a folder in real time. I did start it with SFILTER sample from DDK IFS. I’m filtering IRP->Flags with IRP_NOCACHE to encrypt/decrypt buffer. Thus, the cache will be decrypted rigth? Can I leave Fast I/O unmodified?

Thanks in advance.
Fernando Roberto da Silva.

3

Thanks for your attention.

Regards,
Fernando Roberto da Silva.
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Alexei Jelvis
Sent: sexta-feira, 31 de outubro de 2003 02:16
To: Windows File Systems Devs Interest List
Subject: [ntfsd] Re: FS Filter to Crypt and Fast I/O

Yes, you need to leave Fast IO unmodified. Fast IO is only used to copy
user data to the cache, it is not used to write data directly to disk.

Alexei.
“Fernando Roberto da Silva” wrote in
message news:xxxxx@ntfsd…
Hi all,

I’m writing a FS Filter to encrypt/decrypt files in from a folder in
real time. I did start it with SFILTER sample from DDK IFS. I’m filtering
IRP->Flags with IRP_NOCACHE to encrypt/decrypt buffer. Thus, the cache will
be decrypted rigth? Can I leave Fast I/O unmodified?

Thanks in advance.
Fernando Roberto da Silva.
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4

Since your driver will change the file sizes, this is a huge effort. In fact, you will need not a filter, but a filesystem over another filesystem with different FCBs and Cc/Mm interaction.

Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
xxxxx@storagecraft.com
http://www.storagecraft.com

----- Original Message -----
From: Fernando Roberto da Silva
To: Windows File Systems Devs Interest List
Sent: Thursday, October 30, 2003 9:36 PM
Subject: [ntfsd] FS Filter to Crypt and Fast I/O

Hi all,

I’m writing a FS Filter to encrypt/decrypt files in from a folder in real time. I did start it with SFILTER sample from DDK IFS. I’m filtering IRP->Flags with IRP_NOCACHE to encrypt/decrypt buffer. Thus, the cache will be decrypted rigth? Can I leave Fast I/O unmodified?

Thanks in advance.
Fernando Roberto da Silva.

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To unsubscribe send a blank email to xxxxx@lists.osr.com