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  #1  
Old 12-16-2002, 08:07 PM
w00tz` w00tz` is offline
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Default speaking of steganography

well, i was wondering, i've had this burning question on how one can possible embed secret messages in picture format. the picture can be the same, but inside the picture there might be a secret hidden message written in hex format....im not sure if this is possible, but i would like to hear some feed back on possible opinions, i just think it would be utterly cool if one can do that
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  #2  
Old 12-17-2002, 04:21 AM
Acid_Cool_178 Acid_Cool_178 is offline
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It is possible if you now the format of the picture or the music file, stego can be used in music files also. The diffrence will be the filesize, the orginal file will be smaller than the stego file. And the make it more secur so is it possible to encrypt the message also int here by using some methods like TEA, RSA, DES, AES and so on.
Check out this link http://rr.sans.org/encryption/steganalysis.php

Acid
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  #3  
Old 12-17-2002, 08:20 AM
kw kw is offline
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Quote:
The diffrence will be the filesize, the orginal file will be smaller than the stego file.
Not necessarily.
I think mala mentioned this as an example earlier too, but you could hide the message inside the image itself without people seeing a difference, say by hiding 3 bits of the message in each pixel (in the lowest bit of the r, g and b values). This wouldn't increase the file size at all. Also, on some cases there will be room in the header of the image file where you can simply put stuff.

-kw

PS. Im no expert, I might've misunderstood some things about these techniques, correct me if I'm wrong
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  #4  
Old 12-17-2002, 09:28 AM
mala mala is offline
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Sure, it's possible!

Knowing the specs of a file format (and provided a file which is large enough), you can hide everything you like in any file. One of the greatest things about steganography is that there's not a standard, you can use your brain to create new ways to hide data!

Only for images, there are many ways to "cover" secret messages:

- the easiest way is to use a property of jpg or gif images: their header, at the beginning of the file, gives you the size of the image and every byte you append at the end of the file is ignored during visualization, since they exceed the size (x*y) of the image. So, you can just open the image in a hex editor and add all the data you wish. A funny experiment you can do under windoze is to append a zip file to an image: win uses file extensions to recognize file types, and since zip informations are stored at the end of a file, while image info are at the beginning, you have just one file which opens as image or as zip according to the extension you give to it!

- another way, which is a bit more complex but quite easy to understand, is to hide data in the lower bits of every pixel. How does this work? Since every pixel has, for a 24bit image, 24 bits (really? ) which define its color (8 for Red, 8 for Green, 8 for Blue), you can use the lower bits of each color to hide bits of the hidden message: the change is not visible to human eyes, but you can hide a file whose size is about 1/8 of the number of pixels (x+y) of the image. Also notice that while the previous example made the file bigger, this one gives you a file with the same size.

- a harder way, still on images, is to change DCT (Discrete Cosine Transform) coefficients of JPG images to carry data. Still, the difference is almost unnoticeable for the human eye but you can still hide "many" information.

Well, this is just a little intro... but think that with every thing you can code in bits (upper or lowercase letters, coefficients in audio files, blinkings of your eyes, _everything!_ ) you can hide secret data too!
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  #5  
Old 01-11-2003, 01:11 AM
jeff jeff is offline
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hello mala my friend

i almost didn't sign up; it mentioned several times in other postings, that newbies such as i (in the sense that i AM pretty dang puter illiterate) might not be at the right place, at the right time ... maybe in 20 years if i study only 10 hours a day

Knowing the specs of a file format

i gottah look these things up everytime ... i don't have a good memory since my 2 strokes (where'd i put my beer???)

but a few signatures seem always present within filetypes to note:

a gif file ends in: 00 3b
a jpeg file ends in: ff d9

if i do a search of file in uedit and there is anything AFTER ff d9 or 00 3b (depending on filetype) i am generaly kindah suspicious... especially if the next thingk i see says PK or ...

camouflage usually has its signature too, as well as jpegX
cam== (ff d9 -end file) 20 00 <<--- begin cam
jpeX== 5b 3b 31 53 00

had some notes, don't know where they are ... just thought "signatures" +of might be of note

have a great new year mala! [/i]
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  #6  
Old 01-11-2003, 08:32 AM
AndreaGeddon AndreaGeddon is offline
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hi, time ago (when i studied steganografy) i thought it was really impossible to hack data from such a tecnique, but i found that steganografy could easily be detected by studying the entropy of the target file. For example, a normal picture would have a normal misure of entropy, but in a picture with hidden info the misure of entropy would be greater than normal (in simple terms, the disorder of the bits raises as the picture carries more information in it). Also in audio or video steganografy they were sydying techniques of bit-turbulence-weighted-average, so that you can find a steganografed data by checking the disorder of the possibly affected lsbits which deviates from normal average
Do anybody know what are the latest developments about this?
Bye all!
AndreaGeddon
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  #7  
Old 01-14-2003, 07:15 AM
mala mala is offline
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Quote:
hello mala my friend
Hi jeff! Welcome and thank you very much for your contribution... I had been too involved in browsing with perl and regexps to remember I also deal with steganography

Quote:
Do anybody know what are the latest developments about this?
Yes, there are ways (some quite intuitive, other less) to protect from steganalysis: for instance, you could give a look at

http://www.citi.umich.edu/u/provos/stego/

And after all, you can still try to go around entropy checks just by manipulating the data before you hide them and putting them in a medium which is "big enough".

Ah, I've just fallen into


http://citeseer.nj.nec.com/cs?q=steganography&cs=1

if anyone wants a good reading about stego, it's probably here. I'll review some as soon as I finish the old ones - if you want to contribute with reviews you're welcome ^__^
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  #8  
Old 01-20-2003, 06:23 PM
null null is offline
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Default a little digression

Well, just a little digression ...

Today, my mother cooked a kind of a pie with meat and potatos - very delicious, indeed. Anyway, the filling of this pie contains some pepper, which my little son should not eat, so mama did a great thing. She steganoed a piece without pepper into the pie and to me everything looked as usual. There was just no way to notice it without eating a piece of the pie.

This was the little story. I've just never thought about real-life steganography from this point of view and I wanted to share my thoughts with you. Some of you may have similar experiences, so please let us know about 'em!

Regards!

null
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  #9  
Old 01-21-2003, 02:49 PM
Devine9 Devine9 is offline
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vegetables + grinder + injection into my speghetti/other foods as a child

evil memories
I will to this day not eat mushrooms or olives.. ugh..
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