Steno Update

I was suspended again. Almost 3 weeks this time. But I'm back, I'm bad, and I'm feelin' mighty good about myself.

I spend the time digging into stenography.

My first stop was JPEG. I sucked it up in the first two weeks. Seriously got into DCT/iDCT and quant/de-quant. Have you ever seen a JPEG image in DCT and quant state? It's seriously cool. I was looking for a way to hide information in the coefficents. I tried several different ways but they are all way too volatile for my tastes. So I tried my own method based on deltas (first derivative). Extremely robust, but highly destructive. Give and take don't ya know.

igh:

So then I dug into JPEG2000. I'm sure I can de-construct and re-construct, but JPG2000 is too flexible. Too many ways to do things and nearly zero guarantee that anything will survive quantization. I'm sure it's not quite as bad as it sounds, but I do know that I won't be happy.

Now, there is something about Nam's technique that makes it rather universal with regards to different colour spaces used in different formats. I did identify this trick earlier, but I wanted to play with waveletes and coefficients.

One thing that I did start playing with is FFT/iFFT for steno. OMG this was *so* cool. I might put together a tutorial for this. The only thing is that it leaves a very tell-tale pattern in the image.

So, JPEG and JPEG2000 are no-go and I'm back to Nam's technique. Which is fine because I've always wanted an excuse to dig into JPEG et al. As a matter of fact, this stenography thing is an excuse for something else that I've been working on in the back of my mind. As the GI Joe crew used to say, "Knowing is half the battle."

Back to Nam's technique because of said universal thingy. Still got a bit of tinkering to do under the hood and some testing to make sure I got things straight.

The only thing that bothers me about Nam's technique is hot spots. Not that they exist, but that I'm not sure what is causing them. I have no desire to fix them, but I just gotta know.

If I'm not back in a week, holler. However, there is a good chance I'll pull an all-nighter and hack out b2 by morning.

Again, you will need DevIL.



Nam's Mark b3
PC/Win only



Works almost identitally to b1 on the surface.

Theoretically it will work with scripting and actions, but I haven't tested beyond ctrl+f.
And it will prolly toss out a 1290 error the very first time you run it, which is fine. All you have to do is cancel the error and go about it. Once the pump is primed, so to speak, should be all good.

I did some quick tests with JPEG and JPEG2000 and it looked pretty good to me. However, I'm not exactly sure about the resulting noise when checking for your mark. You can see the mark, but it is rather noisey and I don't know if this is normal or not. I could very well be missing a tiny little something in Nam's technique.

I did not test with TGA, BMP, or PNG. I didn't really see any reason to test these formats, but you never know.

Let me know how it goes and I'll be ready for more tinkering.

I'll also change the name if Nam wants me to and somebody comes up with a suggestion.

Shorthand? Gonna be a court reporter?

"Steganography: it's not an extinct reptile."

I've read it four times myself and still don't have a clue. Passing notes in class?

Steganography is a fancy term for hiding the fact that you're passing an encrypted message by hiding the encrypted text inside a larger message. In the old days spies had to do things like taking the third letter of every word and looking it up in a codebook, so you get something like this:

enrrdecauscsdc...

Which when you feed it through the code book it says:

runcible ok stop sister needs fresh macaroni

Which means the plan to blow up the Houses of Parliment is on track, but the terrorist nuns are running low on ammunition.

OK, now, with modern computer technology you can take the low bits of a picture and hide your encrypted message in them, and it just looks like a little noise in the photograph of a fat guy in a Pokemon costume you just posted to 4chan, so the cops don't know that the picture contains the secret formula for death by embarrassing halitosis gas.

Now, there's not a great market for software to pass secret messages through embarrassing pictures, but people figured out you could use steganography for digital watermarking (which isn't really what Johannes Trithemius had in mind when he coined the term back in the middle ages), in this case putting a different picture inside your picture, so when someone rips the textures from your "Brocade Jacket" and uploads them as his own, you can go to Linden Labs and say "hey, if those are his clothes, how come when you feed the image into this standard watermarking program with the key 0xFE65AD473E it comes up with my logo?"...

Gotcha. Thanks! I understand the concept, and now I know the word for it. I never would have guessed that's what the thread was about, but now I'm enlightentened. I appreciate your explanation, Argent.

/me goes back to the garage to perfect her formula for halitosis gas.......

Okay, last call. If nobody says anything in the next few days, I'm gonna wrap it up and call it good.

Thanks, Abu. Can you give it a week before you call it done? I'd like to play with it, but I'm sick as a dog right now, so I probably wouldn't be able to give it much clearheaded testing. And assuming I'm not still sick by Thursday, I'll be out of town all weekend for a memorial service.

Okay, I'll keep it open longer. No worries.