Encrypt Information In Images Without Distortion

Nomikos writes "C|Net reports: Researchers have created a new way to encrypt information in a digital image and extract it later without any distortion or loss of information. A team of scientists from Xerox and the University of Rochester said that the technique, called reversible data hiding, could be used in situations that require proof that an image has not been altered."

Comments

porn

[Transient0]

So I'll finally be able to verify whether or not that's a REAL picture of Britney Spears getting it on with a dalmation?

SWEET!

Re:This has been done forever.

[Valar]

This isn't really feasible if you are trying to extract the data losslessly. The original image file will not match with the extracted file. There is loss in the printing (ink smudge, low resolution printer), loss in the photography (ambient light, noise on the film, thumb in front of lens) and loss in the scanning process. As a result, even if the scanned image is in the same format as the original, there is still loss.

Encryption?

[heliocentric]

Isn't it more like steganography? I mean, ok, so we can encrypt the message you store using steg. but are we confusing the two?

Re:Encryption?

[nuntius]

From reading the paper (college access to IEEE publications sure is nice), the researchers outline two forms of reversible data embedding.

Type I simply embeds the data into the spectrum of the image and uses modulo addition as necessary to prevent overflow. Unfortunately, this causes "salt-and-pepper artifacts" because this sometimes affects the most significant bits in a pixel's representation.

Type II uses the traditional method of overwriting the least significant bits or high-frequency coefficients in the image (depending on image encoding).

What this paper does is describe a method that employs Type II encoding and saves the overwritten bits by compressing them and inserting into the embedded data stream. Unlike simple Type II encodings such as always using the lowest two bits, this paper varies the number of bits which are used in each byte. This value is determined according to their compressibility and other parameters in the image. By doing this, the paper obtains a more efficient tradeoff between storage and distortion.

The journal article is "Reversible data hiding" in IEEE Internation Conference on Image Processing, 2002, volume 2, pages 157-160 http://ieeexplore.ieee.org/servlet/opac?punumber=8 052

I don't get it...

[RomikQ]

The new technique builds on previous methods but modifies the lowest levels of pixel values using data-embedding algorithms. It allows authorized viewers to extract the embedded authentication message while also removing any distortions created by the embedded information

So while the encrypted data is in the image, the picture is still distorted, it's only when you take the data out, then you get the original. What's the point of that??? I mean that was what it was like before, wasn't it?

By the way, adding plain text to the end of a jpeg file doesn't alter the image in any way, no matter how much you add. So you could encrypt the text you want and add it at the end and there you go, lossless data encryption in images :). Do I get a Nobel prize now?

Is it really encryption?

[verch]

Sounds like 'encrypt' isnt exactly the right word here. Maybe 'encode' would have been better. From the very tech light article it seems that this is a watermarking technique which somehow embeds the watermark with no distortion of the image whatsoever. Traditional watermarks distort the image, albeit usually not noticeable to the casual naked eye.

Re:Holy Cow!! This Is Awesome!

[packeteer]

They are refering to water marks. This is not about "encryption" or even "stenography". The problem is proving a document is original. Normally you put and ugly water mark on the image. With this techinque you can put the water mark in but you also put in data "securly encrypted of course" about how to get the water mark out.

Sheesh i feel dirty now that i have summed up the whole article because people post before they read it.

once again all the early posters got it wrong

[intuition]

This is steganography with the original image hidden in the steganography as well. Hence the term, "reversible data hiding." That way, not only does the current image hold the data you are sending, but you get a copy of the original image (before steganography) as well.

The fact that every poster so far hasn't seen this fact, is a disturbing reminder of what the average poster on slashdot has become.

does anyone have any suggestions as to where to go next?

My bullshit detector is on yellow alert

[Crag]

"For instance, a digital camera that carries the new algorithms could be used to gather forensic evidence for use later in a courtroom. Any subsequent manipulations of the pictures could be detected, and the area where they occurred could be pinpointed."

Whatever the camera is doing at the scene of the crime could be faked in a lab. Even if each camera has its own PGP/GPG key, the picture is only as reliable as the security of the camera and the key.

What they should do is have the crime scene photographer and his superior digitally sign the images at the crime scene. This would remove the image format from the equation and make the data and the image as secure as the keys of the people involved.

Re:My bullshit detector is on yellow alert

[ChristopherLord]

Canon does provide support for a "Data Verification Kit" on its latest 1Ds camera. No word on how secure it is, etc.

from here:
"Finally with a nod toward law enforcement the EOS-1Ds is the first digital camera that offers the ability to verify that images are unaltered originals using the Data Verification Kit DVK-E1, consisting of a dedicated IC card and card reader, together with software for Windows 2000/XP. This package is available to verify that EOS-1Ds image files are absolutely unaltered. "

In other news...

[the_other_one]

The RIAA and MPAA have sponsored new legislation to make images illegal on the internet in the United States. Images have been known to carry illegal circumvention devices such as DECSS. Thus images in themselves are also potential circumvention devices under the DMCA.

This is great!

[seanadams.com]

Researchers have created a new way to encrypt information in a digital image and extract it later without any distortion or loss of information.

So, if I can add some information to an image without any loss of information in the original, then I don't see any reason why I couldn't use this technique repeatedly, ad inifinitum, on the resulting image. Therefore, they have created a way to turn any one of my pr0n jpegs into an unlimited storage device.

This really changes everything we thought we knew about computer science and information theory. What an incredible discovery!

Re:Signed Hash

[packeteer]

Thats where the encryption comes in. The watermark can only be reversed on the correct machine. Think like pgp, only the person you want to can read the email you send. They plan to work this into hardware. They would probably give the hardware a unique key and have the picture creator encrypt so only that key can open it. This way if you say wany a secure presentation you can set it so only the one projector in the white house can read it without the watermark.

"Optimal"

[fireboy1919]

Have you studied any image compression theory? Have you heard of the famed graduate student method for fractal compression?
Here it is
1) Lock a graduate student in a room with an image and a huge collection of mathematical knowledge about fractals
2) Tell him/her to compress the image by finding and modeling fractal patterns
3) Wait four days...
VOILA! 10000x compression is not unheard of with 1% or less degredation.

Ever image format that we use today is sub-optimal. We don't even have a mathematical formalism to perfectly identify the entropy (i.e. information) encoded within an image (though we can make rough estimates) to determine the maximum compression. Also, consider than even given the techniques we have today, jpeg isn't the best thing out there, though it is the standard. jpeg2000 is better, and there are some even more highly sophisticated and accurate wavelet based approaches. If we can ever get the kind of computing power available to the supercomputers of today we can do even better by modeling our images using more complex basis functions than sinusiods and wavelets.

Just one final note to sum up: finding optimal compression is definitely an NP-hard problem. Who knows what kind of stuff can be thrown in there without affecting much.

Steganography

[Chris Burke]

Well, you can blame the editor, but it's really the article's fault. What they're really talking about is lossless steganography, which is a neater trick. The idea is to hide data in a standard (eg. GIF) image, and be able to extract that data while at the same time preserving the entire image. For the applications they talk about (watermarking), the hidden information is encrpyted, which may be why that word showed up.

I'm curious about their claims. Do they claim to be able to hide the data in an existing image format without image loss? For formats like GIF, it'd be tough, because compressed data (by design) lacks the redundant bits Information Theory demands before you can start cramming extra bits of data into the same space. They certainly wouldn't be able to guarantee that the image was without quality loss before removing and correcting for the watermark. ;)

So I guess I'm not sure what they're claiming.

Though I think for the applications they are stating, actual hiding of the data isn't the point. You don't care if people know that there is some data hidden in the image, you only care that they can't read it or forge it. It'd be much easier then, because you could make a new file format. Shit, all you'd have to do is take a .PNG, stick an encrpyted md5 sum at the back, and call it (S)ecurePNG.

Which isn't a bad idea, actually... You could do some of the things they talked about.

For digitizing contracts, both parties would put an md5 sum encrpyted with their private keys in the image of the contract. Anyone (e.g. the Court) can read the md5 sums and verify that a copy of the contract is legitimate.

For verifying forensics photos, the camera they used would have to encrypt all the photos it takes with a private key (the Courts, again?) not known to the police officers who do the work. I think this is unworkable.

The only problem with both of these ideas is that they are only worth as much as you can trust that the private keys have not been compromised. If you're going to be convicting people on the basis of signed police photos, you'd better be damn sure that the police couldn't have possibly discovered the private key hidden in the camera's hardware.

But like I said, this doesn't involve hiding data in a photograph. I'm just wondering what the -purpose- of the steganography was actually supposed to be. Why is it important that the information be -concealed-?