Scientists develop algorithm for ultra-secret security technique

June 13, 2006 feature
Using a security technique called “optical Fresnel image hiding,” scientists can hide a secret image (such as the woman on the right) using algorithm keys that modulate the image’s light amplitude from a host image (such as the tower on the left). In contrast to other optical image hiding methods, the secret image is not embedded into the host image, decreasing the risk of hacking. Image credit: Yishi Shi et al.

To achieve a high capacity security system that is exceedingly robust to attacks, scientists have developed a set of instructions to unlock secret information, avoiding the need for embedding images and the risks involved.

Information theft has become one of the most feared types of theft due to the vast power that comes with possessing certain information. Our numbers – social security numbers, credit card numbers, passwords, bank accounts, etc. – give authorization to access private documents and assets, and attempts to hack such accounts are ongoing.

Optical security, which consists of hiding a secret image and includes methods such as holography and virtual optics, has been a growing field in security over the last few years. Until now, optical techniques have required the embedment of a secret image in a host image. Although a logical hiding procedure, embedded images can often be found in watermarked images, jeopardizing the security of the system. (Watermarks are the visible but difficult-to-replicate marks used to protect against fraud, while the host image is the visible, normally printed image covering the secret information.)

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.

“The phase keys, designed by the phase retrieval algorithm, modulate the amplitude of the input [host] image into the amplitude of the secret image by the two Fresnel transformations,” Yishi Shi, coauthor of the paper in a recent issue of Journal of Optics A, told “The phase keys are the main keys for the extraction of the secret image. The second type of key, the additional optical keys (which include the wavelength key and the mask position key) are also employed in our Fresnel system, which help to achieve a higher security level than can be achieved by Fourier systems.”

This technique, which the scientists call “optical Fresnel image hiding (OFIH)”, satisfies “the three most important requirements in image hiding,” according to the team. Because no embedding occurs – meaning that the secret image cannot be found in the watermarked image – the method satisfies the so-called “imperceptibility requirement.” Since the watermarked image contains no secret information, and the phase keys are the main method for extraction, the OFIH method also satisfies the “robustness requirement.” Finally, since the secret image is the same size as the host image, this method also satisfies the “capacity requirement.”

Another advantage of this optical technique is that one host image can hide several different secret images. In addition, one secret image can be hidden in different host images. These multiple variations further enhance the flexibility and robustness of the system.

“This system is designed as a fragile system that may be used for authentication, and also could be designed as a robust or semi-fragile system for the purpose of image hiding or digital watermarking,” said Shi. “If we adopt the pure digital method to apply the Fresnel system, its realization will much easier. Thus, the flexibility of the designs for different application purposes is also obtained in the OFIH, allowing us to implement the system either by pure digital method or the opt-digital method.”

Citation: Shi, Yishi, Situ, Guohai and Zhang, Jingjuan. Optical image hiding in the Fresnel domain. Journal of Optics A: Pure and Applied Optics. 8 (2006) 569-577.

By Lisa Zyga, Copyright 2006 All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Explore further: The forgotten scientist who paved the way for the discovery of DNA's structure

Related Stories

Monster image of the Fornax Galaxy Cluster

October 25, 2017

Countless galaxies vie for attention in this monster image of the Fornax Galaxy Cluster, some appearing only as pinpricks of light while others dominate the foreground. One of these is the lenticular galaxy NGC 1316. The ...

3-D imaging reveals secrets of immune cells' agility

September 27, 2017

Newly developed microscopy techniques have allowed UC San Francisco researchers to observe white blood cells in action in unprecedented detail. Videos the scientists have created using these advanced microscopes are revealing ...

How Herschel unlocked the secrets of star formation

September 18, 2017

Surveying the sky for almost four years to observe the glow of cold cosmic dust embedded in interstellar clouds of gas, the Herschel Space Observatory has provided astronomers with an unprecedented glimpse into the stellar ...

Recommended for you

How the Earth stops high-energy neutrinos in their tracks

November 22, 2017

Neutrinos are abundant subatomic particles that are famous for passing through anything and everything, only very rarely interacting with matter. About 100 trillion neutrinos pass through your body every second. Now, scientists ...

Lightning, with a chance of antimatter

November 22, 2017

A storm system approaches: the sky darkens, and the low rumble of thunder echoes from the horizon. Then without warning... Flash! Crash!—lightning has struck.

Quantum internet goes hybrid

November 22, 2017

In a recent study published in Nature, ICFO researchers led by ICREA Prof. Hugues de Riedmatten report an elementary "hybrid" quantum network link and demonstrate photonic quantum communication between two distinct quantum ...

Enhancing the quantum sensing capabilities of diamond

November 22, 2017

Researchers have discovered that dense ensembles of quantum spins can be created in diamond with high resolution using an electron microscopes, paving the way for enhanced sensors and resources for quantum technologies.

Study shows how to get sprayed metal coatings to stick

November 21, 2017

When bonding two pieces of metal, either the metals must melt a bit where they meet or some molten metal must be introduced between the pieces. A solid bond then forms when the metal solidifies again. But researchers at MIT ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.