CF & Security Issues

[Stuart Langley]

Hi All,

I am wondering if anybody has put any thought into, or if there is
some information around, regarding device security and integrity when
using CF cards as the storage medium.

I am thinking along 2 main lines here.

1. Somebody removes the CF card while the device is running. Will it
be detected? What is the likely result on the system when the card is
removed? What could happen if a second, different card is plugged in
while the system is still up?

2. Critical files on the CF are replaced with malicious or counterfeit
versions. i.e. a user powers down the device, removes the card,
inserts it into a writer, replaces a couple of files, puts the card
back in the device and powers on.


On point 2 a md5 hash over the device should detect if a file has been
altered, but then that would not prevent the user from replacing the
app that was going to do the md5 checksum in the first place to
prevent this detection from working.

Can anybody help with some ideas/solutions for these issues?

Thanks In Advance,

Stuart

 

[Slobodan Brcin]

1. Most likely system crash (don't know). Protect your card so it is
inaccessible.
2. Depends on the user . Give it to me (and some time of course) and I'll
install you what ever code you like.

Nothing can help you to protect your device.
You can integrate digital signing in application, drivers, etc. But it all
can be bypassed given enough time.


What type of question is this:
Copy protection?
Image tamper detection?
High risk security application?

If high level of money is at stake, then you can try to make live miserable
to someone who try to tamper your image.

Make custom bootloader that support RSA, or some other asymmetric cipher
algorithm.
Use it to decrypt SDI image to memory.
Do ram boot:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnxpesp1/ht
ml/ram_sdi.asp

Also make your drivers and app check independently some digital signature of
their own on boot medium.

This should be reasonable safe to tamper. But someone could swap whole image
with custom image and imitation of program.

What do you want to prevent?

Regards,
Slobodan