The correct place to encrypt or decrypt ANYTHING is just before access to the "outside" world, i.e., in the case of a file-system, the reads and writes to the storage device (disk drive). You are in a world of hurt if you intend to encrypt 'data' and directories separately.
If you need to use an existing file-system and then encrypt it, you use the same technique but your "storage device" is a "container file" that you mount using the loop device. This allows you to have an encrypted file-system below some mount-point and a normal file-system above.
FYI, there are existing tools/code that allow one to mount an encrypted file-system. Perhaps your masters project just got easier?
On Wed, 2 Feb 2005, Vineet Joglekar wrote:
Hi all,
I am trying to add some cryptographic functionality to ext2 file system for my masters project. I am working with kernel 2.4.21
Along with regular files, I intend to encrypt directory contents too. For reading I guess the function ext2_get_page in fs/ext2/dir.c is used. Hence I can put my decryption routine in that function. Is that correct?
I was trying to look for the routine which writes the dentry on disk, but was unable to find it. I found out that the function d_instantiate is used to fill in inode information for a dentry, but unable to see when it is written on disk. I suppose that I have to encrypt the dentry just before writing on to the disk, as if i encrypt it before, other functions using it wont be able to access until they decrypt. So please help me with this, that when and where shall I encrypt the directory contents.
Thanks and regards,
Vineet
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