[Help] How to Replace File Operations in File System?

[freeman.zhang1992@gmail.com (Freeman Zhang)]

Hi,
Sorry about the delayed response. To be frank, I haven't think over
these stuff
seriously. I didn't expect too much about the module at first. Now I
know I was
wrong. I shouldn't  get through it rashly-people are watching on me!
And I  believe I can make it with the help and advice I got from all of
you.
Thank you!

> The first question is - what are you trying to protect against? The
> answer to that will influence your design.
>
> As Bruce Schneier said in the intro to Applied Cryptography:
>
> There are two kinds of cryptography in this world: cryptography that will stop
> your kid sister from reading your files, and cryptography that will stop major
> governments from reading your files. This book is about the latter.
>
> It's one thing to write a silly kernel module that will rot13 your
> files.  It's totally another to design a complete system that works.
>
> Do you need to worry about a directory being open for access to encrypted
> files, and another rogue process on the system simply going and reading
> the files and the crypto doesn't matter? (This is an issue for cryptLUKS,
> for instance - it defends against somebody stealing a powered-off laptop,
> but not against processes that get access to a running system.  You may wish
> to think for a bit about what security is provided by a system that is
> suspended, rather than powered off - particularly in the case of
> cold-boot attacks....)
>
> Do you need to worry about somebody replacing the binary that prompts
> the user for the passphrase before loading it into the kernel, with a
> version that saves the passphrase for later, after the device has been
> "recovered" via theft or similar? (And yes, this *has* been used before,
> see 'FBI v Scarfo', where they installed a keylogger to snag a PGP passphrase:
>
> https://epic.org/crypto/scarfo.html
>
> Do you need to worry about other more generic keystroke loggers?
>
> Do you need to worry about the fact that most user passphrases won't
> have enough entropy to be used directly as crypto keys?  If you merely
> use the passphrase for salting a randomized key (such as the way gpg,
> ssh, and cryptLUKS use your passphrase), how do you address the problem
> of insufficient random entropy at key generation time?
>
> That's just the obvious stuff you will need to worry about. :)
>
Regards
Freeman Zhang
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