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

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.

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?

Don't let Bin Laden read this...

[TheGreenGoogler]

As I recall, the FBI had evidence that Bin Laden was using steganography to conceal messages in photos...

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.

Something doesn't sound right

[plierhead]

The article seems utterly light on some key information (about which file formats etc), but simple information theory suggests that this will only work on less-than-optimal image formats.

Any optimal image format will result in a file only just big enough to store the image and no bigger - and therefore it will not be able to store any additional data without reducing the image quality in some way.

Without any further information available, could it be they are just talking about taking advantage of flaws in some given format such as jpeg ?

Re:Signed Hash

[Xenographic]

A signed hash can be separated from an image, while this type of watermarking cannot.
>>>>>

There must be some way to separate it from the image, as the technique is also supposed to be *reversable*

I'm not sure just what they're up to, though, the article isn't very detailed...

Re:Signed Hash

[notestein]

I'm not sure I believe that. If I wanted an image that is guaranteed to not have been tampered with... A missing signed hash would invalidate the image as much as a changed hash. Now to put the equivalent of a signed hashes data back into an image via an algorithm.... that seems like less security.

Camouflage

[c.emmertfoster]

How is this any different from Camouflage, which is used by some "Warez" sites to hide files within images?

I've seen this used to keep zip files on free-webservers which do not allow them.

Quote from their website: "you could create a picture file that looks and behaves exactly like any other picture file but contains hidden encrypted files"

Re:This has been done forever.

[LinuxInDallas]

I'm assuming that the parent of your message was using a little humor in saying you can simply scan something and retrieve its contents perfectly.

That being said, depending on the type of data you scan you may very well be able to retrieve it all. As a simple example, you can scan a page of plain text and get it all back via OCR with good reliability. I would guess that with a high enough quality scanner you could get pixel-level-accurate scans of a high quality printing. That equipment is probably out of most of our budgets though.

Re:My bullshit detector is on yellow alert

[ngoy]

In addition to the comments above, Epson (who hasn't put out a new digital camera in quite awhile) has had something called IAS (Image Authentication System). Per their web site:
Image authentication is provided from the point of capture and thereafter
EPSON IAS-protected images remain standard JPEG images, viewable with all software programs that read JPEG images
Image manipulation can be detected down to the level of a single bit
Verification of image integrity is fast and easy.
IAS images suffer no visible loss of imaqe quality
Compatible with the EPSON PhotoPC 700, 750Z, 800, 850Z, 3000Z, and 3100Z digital cameras
Works with Windows 95, 98, 2000, Me, XP, and Windows NT 4.0 (with Service Pack 3 or higher)

Not a lot of information, but theirs has been out for a LONG time. It has "non-visible" to the human eye detection, so it should have sufficed for any forensic photographer that could use a 3MP image (which I don't think is sufficient for decent crime scene photography, but I am not a CSI).

I personally do not see where a "lossless" type of authentication is useful, even in medical imaging, is one shade off going to make a difference?

ngoy

Court Evidence Verification? No...

[syphoon]

"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." So if I want to manipulate court evidence, what's stopping me from taking a *screenshot* of the image on screen, manipulating that image, and then re-encoding the hidden data so it appears no editing has taken place?

Detectable?

[FireMage]

My main quetion would be if there is any way to discern between a image holding encrypted data and an unmodified "visual only" image file.

"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.

Re:My bullshit detector is on yellow alert

[ngoy]

I understand the need for detail, but we are talking changes of one bit in a scattered pattern. I have not researched it, but I think greyscale medical imaging is on the 10 bit level, so 1024 different shades of grey. If you change the first (or even second) bit, I doubt a doctor is going to point to that and make a diagnosis on a laser imaged x-ray.

And thanks to our wonderful health care industry, it probably is immaterial anyways since the doctors get paid NOT to refer you to specialists anyways...

ngoy

Re:once again all the early posters got it wrong

[cei]

Nowhere in the source article does it say the encoded values are of the original image. It specifically refers to an "embedded authentication message."

While your message has been modded to +5, it is, in fact, wrong.

Re:Signed Hash

[Krach42]

My interpretation of the article was different. They made it seem that they could sign an image, not encrypt the image. Thus, the image was viewable to all, but it's verifiability was secured through this technique. Being that any alteration done to the picture would cause the signature to fail. It would likely result in the picture being blotched in the area that was altered, as the information that was contained there for both the signature and the previous color value are ruined.

Thus, all those pr0n sites that steal pictures from each other, and post them on their own site with nifty looking "pr0n.net" marks would be verifiably altered.

And this is hard because ....?

[mr3038]

If this works with lossless image formats, here's a simple way to achieve the same. I haven't read the paper so this could be practically same they're doing. For simplicity I describe a way to embed 8 bits of data in every pixel in a 24bit image.

1. Extract some LSBs from every pixel from all RGB components (3 from R, 2 from G, 3 from B) and generate a stream from those bits.
2. Append your secret message in the stream generated in the previous step.
3. Compress the stream with any algorithm (e.g. bzip2) and make sure you get size in bytes less than or equal to number of pixels in the original image[1]. Pad with zeros if size of compressed stream is less than number of pixels in the image.
4. Combine the stream with the image inserting bits from the stream to positions where we extracted bits in the first step and save the image any lossless way to want. The image quality will be reduced roughly to the same quality as 16 bit version would be but the original image can be restored from the compressed substream. During decompression, first there'll equally many bytes of image data as there're pixels in the original image and all the remaining data is the embedded message.

[1] This is possible because all natural images have very little information in the LSBs of every pixel and those should compress well. If the image is truly random down to LSB there's no way any algorithm can embed extra information in those pixels.

This will be probably patented. At least this is a bit more complicated than sideways swinging.