New Optical Security Doesn't Require Embedment

An anonymous reader writes "Scientists are claiming to have a new type of optical security that doesn't require embedment. Optical security includes many different options but up until now they have all required that the secret image be embedded in a host image which left it vulnerable. From the article: 'To address this problem of finding the secret image in the watermark, scientists have developed a new optical security method that doesn't require embedment. Instead, the technique uses a phase retrieval algorithm to generate specific optical and phase keys that extract the secret information when applied. The optical keys contain information and are distributed to an individual through a personal identification number (PIN). The information contained in the phase keys (the main source for determining extraction) is distributed to the individual separately.'"

Comments

Does anyone actually understand this?

[TempeTerra]

Ok, so I read the article. Not much clue there. I thought to start with that they were talking about some kind of steganography, but the article claims that the encoded message isn't embedded in the image. It's not a digital image either, (jpeg etc) it's a printed image. As far as I can tell they're using some optical properties of the image as a key to decode some other encrypted data. Hardly an earth shattering technique, but the linked article is just a brief, confusing write-up of an optical physics paper - perhaps there's actually something interesting in the paper that got dropped along the way.

Re:Does anyone actually understand this?

[Aceticon]

The article is indeed about stenography.

Scientists developed a new way of hidding images inside other images, in which, if understood it right, both images are treated as complex waves, and the image to be hidden is amplitude modulated into the waveform of the host (carrier) image. This is a bit similar to how sound waves are modulated into the carrier wave in radio transmission, only in this case the carrier wave is not a fixed frequency wave.

The modulation of the image to hide into the host image is controlled via a phase key. The phase key used in the modulation of the hidden image into the host image is required to extract the hidden image from the encoded image.

Also, this method allows adding multiple hidden images to the host image, as long as they have different phase keys.

How exactly this is beter (in terms of avoiding that an attacker can get the hidden image) than encrypting the image to hide and then merging the resulting data stream into the host image in a straightforward way (for example, using the least significat digit of every RGB value) i don't know (the article doesn't cover it). I suspect this new method might be more rubust when transformations are applied to the encoded image, such as compression, cropping, etc...

Re:Embedment?

[DanQuixote]

The difference is that the image and the message are transmitted separately. This means that you can publicly send a large data set (say a CD full of images) and then privately send information that will decode a message. The private part only has meaning when applied to the proper public image. Perhaps this means one could use an image as a password...