Blocking Steganosonic Data In Phone Calls 185
psyced writes "Steganography is a technique to encode secret messages in the background noise of an audio recording or photograph. There have been attempts at steganalysis in the past, but scientists at FH St. Pölten are developing strategies to block out secret data in VoIP and even GSM phone calls by preemptively modifying background noise (link is to a Google translation of the German original) on a level that stays inaudible or invisible, yet destroys any message encoded within. I wonder if this method could be applied to hiding messages in executables, too."
As the tag says: encryption. (Score:4, Insightful)
Re:Not going to work.... (Score:5, Insightful)
Maybe they will use the foreground noise -- for example, they could alter the pitch of the speaking voice to precisely fall into certain discrete frequency ranges, and then they occasionally bump a couple of samples into an 'unused' range and use those as a simple binary encoding of the secret data.
If they use enough discrete frequency ranges, the general tone of the speaker's vioce won't be noticeably different and the occasional minor shifts in frequency for the encoded data will hardly stand out.
That is just one example that I literally thought up in 30 seconds. I'm sure someone who was really concentrating could come up with much better ways to defeat the described countermeasures.
Re:Not going to work.... (Score:5, Insightful)
Given that this project is (according to TFA) partnered by the Ministry of Defence, this smells to me like someone spending a lot of money defending against a non-existent threat. What's the betting they used the magic word "terrorism" in their grant application?
Re:Not going to work.... (Score:1, Insightful)
Fundamentally flawed (Score:3, Insightful)
Obscuring data equals obscuring the patterns. So, to obscure the data within a 0 and 1 pattern, you might switch around the 0s and 1s.
For a message embedded in the background noise in a phone call, data may be modulated as 'loudness of background noise within a certain frequency range' or whatever. Obscuring this would be to add random data in the frequency range or whatever.
But that actually takes knowledge of the pattern used. If the pattern is rather the speaker knocking on a table, then any method designed to obscure background noise wouldn't register it or obscure it. It's similar to a scrambling technique that randomizes the 0s and 1s on a diskette sent in the post, while the actual message may be morse code holes punched in the plastic.
Conclusion: To void steganographic data, you need to know the method used to embed it.
Hiding information in an executable is easy (Score:3, Insightful)
You can also reverse the order of many comparison operations as long as you also modify the following branch/set instructions.
If you want to jam such a channel you would have to do the same job, first identifying all the possible locations for such transformations, then randomly flip half of them.
(Un?)fortunately neither the encoding nor the jamming process can be totally secure, because you can check (or know up front) which compiler had generated the original executable, then decompile/recompile and check which encodings the compiler tend to use.
Terje
Re:Not going to work.... (Score:3, Insightful)
I like parent's sig (Score:3, Insightful)
I see the parents sig as a sort of darwinian filter on how careful one is the slashdot reader at clicking link.
Re:Not going to work.... (Score:5, Insightful)
(More) deniability.
Steganography and watermarking. (Score:5, Insightful)
The interesting thing is who is on which side of the battle.
Generally it's corporations who like the idea of watermarks, and individuals who don't. Individuals do however like steganography, but the authorities don't. It will be interesting to see who develops what technologies and who, if anyone, wins this arms race.
Re:Not going to work.... (Score:3, Insightful)
I doubt the CIA will investigate every no carrier joke on slashdot, and if they di^H^H^H^H^H^ 01101000 01110100 01110100 01110000 00111010 00101111 00101111 01110111 01110111 01110111 00101110 01111001 01101111 01110101 01110100 01110101 01100010 01100101 00101110 01100011 01101111 01101101 00101111 01110111 01100001 01110100 01100011 01101000 00111111 01110110 00111101 00101101 01011000 01101110 00111001 00110100 01100110 01110001 00111000 01000011 01010101 01101011 ^H^H NO CARRIER
Re:Steganography and watermarking. (Score:1, Insightful)
DRM - bad
Encryption - good
User tracking - bad
Browser history - good
"Phoning home" - bad
Automatic updates - good
Rootkits - bad
Game anti-cheat sytems - good
GSM already *has* crypto on the calls (Score:2, Insightful)
A mobile-to-mobile call almost always (unless you're both on the same tower) needs to pass over a landline, and to do that, it needs to be unencrypted.
Re:Not going to work.... (Score:4, Insightful)
It's against the people itself. It's propaganda to keep the "terror" alive in memory, generating visions of terrorist so advanced we have to process and inspect all telecommunication, so you can feel safe.
Please, have a look at this documentary: The century of the self [bbc.co.uk].
Why block? (Score:3, Insightful)
That said, it is relatively easy to disrupt stego by lossy compression/decompression or vice-versa if the source is compressed. Low-order bits will get stripped in JPEGs & MP3s. This obviously doesn't work for loss-less compression as is needed for binaries. If hash or other non-compressibles found, just rehash. Once you've decided to meddle inthe datastream, some eggs will get broken. You'll have both alpha and beta errors (misses and false postives).
Re:Not going to work.... (Score:5, Insightful)
Because, they can tell when you send an encrypted e-mail.
The whole point of steganography is to embed the secret message in something you broadcast in the clear, and have nobody be any the wiser that you are, in fact, sending hidden data. You give up your covertness when you observably send something secret. If nobody knows you sent it, they're not looking for it. They just think you were talking about your aunt's petunias.
Think of it as analogous to fieldcraft for spies -- you're supposed to be able to do something completely innocuous so that they can't ever confirm that you've actually done something nefarious.
This system is trying to preemptively just eliminate the ability to send something embedded in a clear-channel communication. Basically, take away your ability to send an encrypted sub-channel in your normal conversation.
Cheers
Re:Not going to work.... (Score:3, Insightful)
Far far easier than trying to secretly encode a message in the background of my audio phone call, and no special gear needed.
Wow are the "spies" of the world getting incredibly lazy? I can come up with at least 30 ways to get around this, one of which is having several prepay disposable cellphones to get around them even tapping my phone call.
Re:Not going to work.... (Score:3, Insightful)
Just as a degenerate example of a little thought experiment...what if I use PKE to encrypt a message to the person on the other end of the line and then write it out in hex? The conversation would go something like: "A! F! 3! 8! 8! 4! 9! BEEEEE!!!"
This is, of course, the most trivially stupid possible way to do this. Much better would be to write a small program that translates the encrypted message to, say, base-256 and then bleeps short tones in one of 256 different frequencies to the receiver program, which collects and decodes the message (with some extra tones reserved for ECC, of course). They don't even need to be fixed tones, I could set the baseline with a tone pattern up front.
You know, the neat thing about sound is that you can send multiple tones at once. Instead of one tone at a time, I could easily figure out a way to time-pack the signals so tones can be played simultaneously or overlap.
Of course, the whole point of steganography is to transmit an encoded message with Eve being none the wiser that such a message was even transacted. So I suppose we'd have to choose a set of words out of the dictionary that map to a particular set of tones, and then design a conversation in which those words are present in the right order. I could easily send this one-time pad to my target (as an encrypted email attachment, of course) in the form of a key that can easily be plugged into a voice recognition program that picks up those words and decodes the message.
There's only like a million ways to defeat such an idiotic thing. Why are they so interested in preventing me from communicating in private anyway? (Hey, yea, that's a good question severoon!)