6 ms·

The TCHunt program, whose website this link points to, is quite interesting. It seems to exist to simply point out something I always felt was self-evident, yet

The TCHunt program, whose website this link points to, is quite interesting. It seems to exist to simply point out something I always felt was self-evident, yet I commonly see misunderstood: "Q. Why write a program such as TCHunt? A. To demonstrate that while encrypted volumes may be indistinguishable from random data created in one specific fashion that the volumes themselves can be easily distinguished from most other files on your system. Many people insist that their encrypted volumes are undetectable. I hope TCHunt will convince them otherwise, before they learn this fact the hard way. More importantly, you should never claim that an encrypted volume with a mp3 file extension (or whatever) is a corrupt file, etc. While that explanation may seem plausible to an average person, it will not stand up to forensic or legal scrutiny. Data corruption does not resemble AES encrypted data. If disclosing the location of your encrypted volumes may lead to legal issues, then say nothing and contact a competent lawyer." Of course, as he notes, it can't tell the difference between regular and hidden volumes, but once again: the hidden volumes will still stick out like a sore thumb and clearly be encrypted data. While plausible deniability is technically maintained, believable deniability will always be harder.

altrego99 15y ago
Basically, it identifies the randomness of a file that is AES encrypted. In general no other file will have that kind of random data. I wonder then, can there be an efficient encryption algorithm which will make your file look more like a particular type of data (say .mp3 or .jpg)?
- jamesaguilar 15y ago
  Well, you could always encode the data as an mp3. If you did, it would look a lot like an MP3. Might not be efficient though. And it would still be easy to tell that it was encrypted data.
  - LeonB 15y ago
    for example, record an mp3 where you sing the 1's and 0's that comprise the encrypted data.
- dedward 15y ago
  This is why you use full disk encryption with a hidden volume, and follow proper practices for keeping both maintained. The computer will be obviously encrypted - but, if done correctly, there will be no way to know there is more than one system in there. (there are plenty of side-channel give-aways though that a thorough investigation might turn up - truecrypt's docs and site explain this better than I ever could) That was off topic - your idea, it is interesting. I wish I had the background to comment on it.
  - icebraining 15y ago
    The problem with full disk encryption with an hidden volume is that if any program starts writing over the 'invisible line' of the normal volume (by which I mean, the size you configured for it), it'll overwrite the hidden data.
drivebyacct2 15y ago
"the hidden volumes will still stick out like a sore thumb and clearly be encrypted data" I thought that was the entire point of the hidden volume... that from outside you can't tell there is a hidden volume? And that from inside the fail-safe, you still can't tell there's a hidden volume? I may simply be mistaken. --- Uh, I think you're missing the point of how the plausible deinability works. The point is that under duress you can acknowledge that it's a TrueCrypt volume, and open it up without at all exposing the hidden volume inside. It's like having a treasure chest with a false bottom where you store your good. The fact that it can't differentiate the location of hidden volumes is... paramount. A "hidden volume" does not mean a truecrypt volume disguised to look like a normal windows file which is what this program looks for...
- carbonica 15y ago
  You're right in a way - TrueCrypt fills empty space in its volumes with random data, and hidden volumes fill that space, and will appear random as well (being encrypted). The question is whether, upon finding a volume which is vastly oversized compared to the non-hidden data, you believe that there are no hidden volumes. If your hidden volume is small relative to your normally-encrypted volume, your believable deniability is much better. But if the important stuff is all on the hidden volume...
  - drivebyacct2 15y ago
    I misunderstood. I see your point now, but I still see good alternatives. Use an external hard drive, easy excuse for having a large encrypted drive. Tell them you just started using it, or made it big and then never decided to use it again, etc.
    - carbonica 15y ago
      Of course having an external hard drive works... as long as you're confident enough to lie well. Hopefully you paid cash, otherwise, they'll know when you bought it. That means no NewEgg. Damn. Then, you just need to be comfortable saying that you bought a 1TB hard drive, encrypted the whole thing (despite the obvious speed hit it'll take, which you know if you're smart enough to use TC), just to throw a few gigs of porn on it. Hopefully you have a wife or significant other, since no single guy is going to encrypt his porn. Not sure how women treat their porn stashes; it just has to be believable. Also, make sure you don't load the porn on all at once - that'll be very, very suspicious. It'll have to look like an organically-grown stash. Given all that, if you can lie well, you might be able to convince an investigator that you (as a suspect in something) have an innocent hard drive on your hands. And you should practice, because if the cops aren't convinced and can't force you to hand over the password (due to plausible deniability), you'll probably need to convince a jury.
ineedtosleep 15y ago
I get that hidden volumes will stick out, but what about hidden volumes that are relatively small in size -- let's say about 500K - 1MB? Would that still stick out as its footprint is smaller or is that not the right way to look at hidden volumes?
- fleitz 15y ago
  Structured data has a 'histogram' that is vastly different than CBC encrypted data. CBC encrypted data has a 'flat' histogram, where as structured data has a different signature. Create a program that creates data histograms and you'll see what I mean. There are much easier ways to tell as well, like FOURCC or magic bits for files, for instance a gif file always starts with GIF89, or JPEGs start with JFIF, same with zip files, tar, etc. Almost every file can be recognized independently of it's name, by it's structure. If you reverse engineer stuff sometimes you'll be given files that you don't even know the structure of and have to figure out what are offsets and what is data. Samething with reverse engineering compiled code.
  - aw3c2 15y ago
    I found the idea of file histogram very interesting so I searched and found this nicely working Python script: http://www.cutawaysecurity.com/blog/file-content-histograms http://www.cutawaysecurity.com/blog/file-content-histograms (needs Python2)
zobzu 15y ago
It's still valid if the entire volume is encrypted that way, aka the disk is 100% random data, then nothing will stand out. The volume might have been deleted by dd if=/dev/urandom of=/dev/sdb (for example) in order to wipe the data and make recovery harder. It's common practice (except you usually want many passes). This is also possible to do on a single partition. Note that this does not mean that TC is undetectable in any way. This only means, that the theory behind the concept is perfectly viable and correct - unlike what you are suggesting.
noduerme 15y ago
Just out of curiosity, I wonder what happens if you zip and tarball your encrypted archives. If TCHunt mimics whatever the standard enforcement scan is, say when you land at an American airport and they search your laptop, then maybe a few rounds of various forms of compression would smooth out the noise?
- __rkaup__ 15y ago
  Do they scan your laptops now?
  - brown9-2 15y ago
    No.
    - jellicle 15y ago
      Unfortunately the answer is not "no", but rather "no for most people, yes for some people".
      - brown9-2 15y ago
        I am curious about this - can you link me to some stories of regular traveler's having their laptop hard drives scanned by the TSA?
        barrkel 15y ago
        Look up Jacob Appelbaum aka ioerror.
        slowpoke 15y ago
        Jacob Appelbaum (of the Tor project) has been detained multiple times at the US border already, and at least one time has had his electronic equipment taken away. The wikipedia article about him has a section about it that should lead to some more sources: http://en.wikipedia.org/wiki/Jacob_Appelbaum#Investigation_and_Detainment http://en.wikipedia.org/wiki/Jacob_Appelbaum#Investigation_a... Granted, he's not a "regular traveler", but then again, it shouldn't matter if you're famous or not.

altrego99 15y ago

Basically, it identifies the randomness of a file that is AES encrypted. In general no other file will have that kind of random data. I wonder then, can there be an efficient encryption algorithm which will make your file look more like a particular type of data (say .mp3 or .jpg)?

jamesaguilar 15y ago
Well, you could always encode the data as an mp3. If you did, it would look a lot like an MP3. Might not be efficient though. And it would still be easy to tell that it was encrypted data.
- LeonB 15y ago
  for example, record an mp3 where you sing the 1's and 0's that comprise the encrypted data.
dedward 15y ago
This is why you use full disk encryption with a hidden volume, and follow proper practices for keeping both maintained. The computer will be obviously encrypted - but, if done correctly, there will be no way to know there is more than one system in there. (there are plenty of side-channel give-aways though that a thorough investigation might turn up - truecrypt's docs and site explain this better than I ever could) That was off topic - your idea, it is interesting. I wish I had the background to comment on it.
- icebraining 15y ago
  The problem with full disk encryption with an hidden volume is that if any program starts writing over the 'invisible line' of the normal volume (by which I mean, the size you configured for it), it'll overwrite the hidden data.

drivebyacct2 15y ago

"the hidden volumes will still stick out like a sore thumb and clearly be encrypted data" I thought that was the entire point of the hidden volume... that from outside you can't tell there is a hidden volume? And that from inside the fail-safe, you still can't tell there's a hidden volume? I may simply be mistaken. --- Uh, I think you're missing the point of how the plausible deinability works. The point is that under duress you can acknowledge that it's a TrueCrypt volume, and open it up without at all exposing the hidden volume inside. It's like having a treasure chest with a false bottom where you store your good. The fact that it can't differentiate the location of hidden volumes is... paramount. A "hidden volume" does not mean a truecrypt volume disguised to look like a normal windows file which is what this program looks for...

carbonica 15y ago
You're right in a way - TrueCrypt fills empty space in its volumes with random data, and hidden volumes fill that space, and will appear random as well (being encrypted). The question is whether, upon finding a volume which is vastly oversized compared to the non-hidden data, you believe that there are no hidden volumes. If your hidden volume is small relative to your normally-encrypted volume, your believable deniability is much better. But if the important stuff is all on the hidden volume...
- drivebyacct2 15y ago
  I misunderstood. I see your point now, but I still see good alternatives. Use an external hard drive, easy excuse for having a large encrypted drive. Tell them you just started using it, or made it big and then never decided to use it again, etc.
  - carbonica 15y ago
    Of course having an external hard drive works... as long as you're confident enough to lie well. Hopefully you paid cash, otherwise, they'll know when you bought it. That means no NewEgg. Damn. Then, you just need to be comfortable saying that you bought a 1TB hard drive, encrypted the whole thing (despite the obvious speed hit it'll take, which you know if you're smart enough to use TC), just to throw a few gigs of porn on it. Hopefully you have a wife or significant other, since no single guy is going to encrypt his porn. Not sure how women treat their porn stashes; it just has to be believable. Also, make sure you don't load the porn on all at once - that'll be very, very suspicious. It'll have to look like an organically-grown stash. Given all that, if you can lie well, you might be able to convince an investigator that you (as a suspect in something) have an innocent hard drive on your hands. And you should practice, because if the cops aren't convinced and can't force you to hand over the password (due to plausible deniability), you'll probably need to convince a jury.

ineedtosleep 15y ago

I get that hidden volumes will stick out, but what about hidden volumes that are relatively small in size -- let's say about 500K - 1MB? Would that still stick out as its footprint is smaller or is that not the right way to look at hidden volumes?

fleitz 15y ago
Structured data has a 'histogram' that is vastly different than CBC encrypted data. CBC encrypted data has a 'flat' histogram, where as structured data has a different signature. Create a program that creates data histograms and you'll see what I mean. There are much easier ways to tell as well, like FOURCC or magic bits for files, for instance a gif file always starts with GIF89, or JPEGs start with JFIF, same with zip files, tar, etc. Almost every file can be recognized independently of it's name, by it's structure. If you reverse engineer stuff sometimes you'll be given files that you don't even know the structure of and have to figure out what are offsets and what is data. Samething with reverse engineering compiled code.
- aw3c2 15y ago
  I found the idea of file histogram very interesting so I searched and found this nicely working Python script: http://www.cutawaysecurity.com/blog/file-content-histograms http://www.cutawaysecurity.com/blog/file-content-histograms (needs Python2)

zobzu 15y ago

It's still valid if the entire volume is encrypted that way, aka the disk is 100% random data, then nothing will stand out. The volume might have been deleted by dd if=/dev/urandom of=/dev/sdb (for example) in order to wipe the data and make recovery harder. It's common practice (except you usually want many passes). This is also possible to do on a single partition. Note that this does not mean that TC is undetectable in any way. This only means, that the theory behind the concept is perfectly viable and correct - unlike what you are suggesting.

noduerme 15y ago

Just out of curiosity, I wonder what happens if you zip and tarball your encrypted archives. If TCHunt mimics whatever the standard enforcement scan is, say when you land at an American airport and they search your laptop, then maybe a few rounds of various forms of compression would smooth out the noise?

__rkaup__ 15y ago
Do they scan your laptops now?
- brown9-2 15y ago
  No.
  - jellicle 15y ago
    Unfortunately the answer is not "no", but rather "no for most people, yes for some people".
    - brown9-2 15y ago
      I am curious about this - can you link me to some stories of regular traveler's having their laptop hard drives scanned by the TSA?
      - barrkel 15y ago
        Look up Jacob Appelbaum aka ioerror.
      - slowpoke 15y ago
        Jacob Appelbaum (of the Tor project) has been detained multiple times at the US border already, and at least one time has had his electronic equipment taken away. The wikipedia article about him has a section about it that should lead to some more sources: http://en.wikipedia.org/wiki/Jacob_Appelbaum#Investigation_and_Detainment http://en.wikipedia.org/wiki/Jacob_Appelbaum#Investigation_a... Granted, he's not a "regular traveler", but then again, it shouldn't matter if you're famous or not.