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WO2006001012A2 - Chiffrage et dechiffrage de donnees de phase geometrique - Google Patents

Chiffrage et dechiffrage de donnees de phase geometrique Download PDF

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Publication number
WO2006001012A2
WO2006001012A2 PCT/IL2005/000675 IL2005000675W WO2006001012A2 WO 2006001012 A2 WO2006001012 A2 WO 2006001012A2 IL 2005000675 W IL2005000675 W IL 2005000675W WO 2006001012 A2 WO2006001012 A2 WO 2006001012A2
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WIPO (PCT)
Prior art keywords
data
images
orientations
polarizer
carrier
Prior art date
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Ceased
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PCT/IL2005/000675
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English (en)
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WO2006001012A3 (fr
Inventor
Erez Hasman
Gabriel Binner
Avi Niv
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Technion Research and Development Foundation Ltd
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Technion Research and Development Foundation Ltd
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Filing date
Publication date
Application filed by Technion Research and Development Foundation Ltd filed Critical Technion Research and Development Foundation Ltd
Publication of WO2006001012A2 publication Critical patent/WO2006001012A2/fr
Anticipated expiration legal-status Critical
Publication of WO2006001012A3 publication Critical patent/WO2006001012A3/fr
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K1/00—Secret communication

Definitions

  • the present invention relates to encryption. More particularly it relates to optical encryption method and device based on geometrical phase, which is originated from polarization manipulation. A space- variant subwavelength grating element is used as a carrier of the encrypted information.
  • optical encryption technique One of the processes that has been extensively investigated is the optical encryption technique.
  • advantages of optical encryption over conventional digital encryption include real time encryption, high space-bandwidth product, difficulty in unauthorized decryption, portability and the possibility of using biometrics.
  • Different optical encryption schemes have been suggested, for example schemes involving pure amplitude image encryption (see P. Refregier and B. Javidi, Opt. Lett. 20, 767 (1995)).
  • Polarization encryption provides additional flexibility in the key encryption design by adding a polarization state manipulation to the conventional phase and amplitude manipulation used in the former methods. This feature is advantageous as it makes the polarization encryption method more secure.
  • geometrical phase modification originate from polarization state manipulation, as anticipated by Pancharatnam (1956) and Berry (1984). Recently, we demonstrated the formation of complex polarization state manipulation by using computer-generated space-variant subwavelength dielectric gratings (A. Niv, G. Biener, V. Kleiner and E. Hasman, Opt. Lett. 29, 238 (2004)).
  • a method for encryption of an input data comprising: producing carrier for the data in the form of a space- variant subwavelength grating element, with local gratings having angles of orientation corresponding to the data. Furthermore, in accordance with some preferred embodiments of the present invention, the method further comprises: illuminating the carrier by a polarized incident beam; polarizing an emerging beam by a polarizer to obtain at least three images of the emerging beam acquired under different polarizer orientations; analyzing said at least three images to obtain a geometrical phase corresponding to the data.
  • the method further comprises applying a key function on the input data to obtain the data to be carried by the carrier, and after analyzing the images based on knowledge of the key function retrieving the input data.
  • the different polarizer orientations comprise two orthogonal orientations and one intermediate orientation.
  • the method further comprises applying a key function on the input data to obtain the data to be carried by the carrier.
  • the method further comprises: illuminating the carrier by an incident beam; polarizing an emerging beam by a polarizer to obtain at least three images of the emerging beam acquired under different polarizer orientations; and using said at least three images as carriers of the data. Furthermore, in accordance with some preferred embodiments of the present invention, the method further comprises: simulating illumination of the carrier by an incident beam and simulating polarization of an emerging beam to obtain at least three images of the emerging beam acquired under different polarization orientations; and using said at least three images as carriers of the data data. Furthermore, in accordance with some preferred embodiments of the present invention, said at least three images are watermarked.
  • the method further comprises: illuminating the carrier by a polarized incident beam; polarizing an emerging beam by a polarizer to obtain two pairs of images of the emerging beam, each pair acquired using different polarization states of the incident beam, and each image of the pairs acquired under different orientations of the polarizer; and analyzing said two pairs of images to obtain a geometrical phase corresponding to the encrypted data.
  • a device for carrying encrypted data comprising a space-variant subwavelength grating element, with local gratings having angles of orientation corresponding to the encrypted data.
  • the element is reflective.
  • the element is transmissive.
  • the gratings are made of dielectric material.
  • the gratings are made of metallic material.
  • a decrypting apparatus for decrypting encrypted data carried by a space- variant subwavelength grating element, with local gratings having angles of orientation corresponding to the encrypted data, the apparatus comprising: a light source for providing a light beam to illuminate the grating element; at least one polarizer for polarzing an emerging beam from the grating element in at different polarizer orientations; an imaging device for acquiring images acquired under different polarizer orientations of the emerging beam.
  • Figure Ia is an exemplary decryption arrangement, in accordance with a preferred embodiment of the present invention.
  • Figure Ib is an example of an input data, in the form of an image to be encrypted.
  • Figure 1 c illustrates the representation of the image of Fig. Ib after it was subjected to a secured key funcition.
  • Figure Id depicts an example of a space- variant subwavelength grating element, made according to a preferred embodiment of the present invention, based on the encrypted input information of the image shown Fig. Ic. L2005/000675
  • Figure 1 e depicts the space- variant polarization direction emerging from a space- variant subwavelength grating element.
  • Figures 2a, 2b and 2c show three intensity pictures obtained by three different orientations of a polarizer used in a computerized simulation of the method of the present invention.
  • Figures 3 a, 3b and 3 c show watermarked intensity pictures for three polarization orientations 0°, 45° and 90° respectively.
  • Figure 3d shows a properly decrypted image when using the watermarked images in the decryption process with the correct geometrical phase key.
  • Geometrical phase encryption can be optically realized by using a PBOE, which results in a robust and stable element that can be achieved using a single lithographic process. Therefore, this method is suitable for chip integration and can also be applied to personal security cards, e.g., credit cards or identification cards, without limiting other possible uses.
  • Geometrical phase encryption can also be implemented digitally, by computerized simulation. An important advantage of the digital implementation is the ability to use watermarking. The watermarking process is discussed later in this specification.
  • a primary input data for example an image
  • a PBOE that encodes the image intensity subjected to a secured key function.
  • the PBOE which is a space-variant rotating wave plate, imprints the image intensity plus the key function in the local orientations of the wave plate's fast axes.
  • the result is a space-variant subwavelength grating element (PBOE), with local gratings having angles of orientation corresponding to the encrypted data.
  • Fig. Ic which depicts an example of a space- variant subwavelength grating element, whose grating orientations (shown in Fig. Id) represent the encrypted information on the element.
  • the input data can be a matrix of any number dimensions, a string, or other form of information arrangement.
  • the information may be discrete or continuous.
  • the secured key function itself may be any key function that is acceptable by the user of the encryption method suggested herein, and in fact the present invention may also be implemented without using a secured key function.
  • the carrier the PBOE
  • the PBOE will be carrying information that can be recognized immediately in the decryption process, without having to be subjected to the corresponding secured key decryption. This means that the encryption of the input information is only subjected to medium change by way of transforming into geometrical phases on the PBOE, and once the geometrical phases of the PBOE are retrieved the in the decryption process the holder of this retrieved information will have the input data at his disposal.
  • the PBOE may be reflective, so that incident light illuminated on it emerges on the same side of the incident light source, or it may be transmissive, so that incident light illuminated on it emerges from the other side of the element.
  • Decryption is performed by illuminating the encrypted PBOE with a circularly polarized light from a light source and retrieving the primary image by analyzing the emerging Stokes parameters with the correct key, as shown in Fig l(a).
  • PBOEs are considered to be wave plates with constant retardation and space varying fast axes, the orientation of which is denoted by ⁇ (x,y). It is convenient to describe PBOEs by using Jones calculus.
  • a PBOE with a space-varying wave plate orientation function of Q (x,y) encodes the primary image of young Einstein, depicted in Fig. Ib.
  • the total orientation function of the wave plates, comprising the encrypted PBOE is shown in grayscale in Fig. Ic.
  • the emerging field which is a result of the vectorial self-interference, is a space varying polarized field. As can be seen, the orientation of the arrows is random.
  • the geometrical phase key, ⁇ k scrambles the space- variant polarization state of the beam and thus randomizes the geometrical phase encoding the primary image, ⁇ ..
  • the Stokes parameters of a fully polarized light (S 0 -S 3 ) are calculated from three intensity measurements. These measurements are taken when the transmitted light is passed through a polarizer with its axis oriented at 0° (/ 0)0 ), 45° (/ 45 ,o) and 90 ° (/90,0). A camera is used to capture the intensity pictures.
  • the subwavelength grating behaves as a uniaxial crystal with the optical axes parallel and perpendicular to the subwavelength grooves. Therefore, by fabricating locally periodic subwavelength structures for which the orientation of the subwavelength grooves is space varying, we achieve spatially rotating wave plates.
  • the realization procedure of the PBOE involves the fabrication of a computer-generated space- variant subwavelength-grating mask.
  • Figure l(d) is a magnified illustration of the subwavelength grating mask of the encrypted element. In order to test the concept, we used a computer simulation. For the encryption process we simulated a PBOE, encrypting the primary image intensity depicted in Fig. l(b).
  • Figures 2(a)-2(c) show the three intensity pictures obtained by the three different orientations of the simulated polarizer.
  • the three intensity pictures can be achieved optically using the realized PBOE, a polarizer and a CCD (see Fig. l(a)).
  • the authorized receiver is able to decrypt the primary image by calculating the Stokes parameters from the three intensity pictures and inserting these values into Eq. (3), along with the correct key.
  • a great advantage of the digital implementation approach is the possibility of using watermarking.
  • FIG. 3(a)- 3(c) show the watermarked intensity pictures for the three polarization orientations 0°, 45° and 90° respectively, while Fig. 3(d) shows the properly decrypted image when using the watermarked intensities in the decryption process with the correct geometrical phase key.
  • the advantage of the later method is that the birefringent parameters of the encrypted elements are not required, thus the method is insensitive to spatial fabrication errors and can be used with incoherent, polychromatic and, unpolarized illumination. These two methods use digital key when decrypting an image.
  • An other approach for discribing a subwavelength grating is the Stokes- Mueller fomalism approach.
  • a uniform wave plate where the fast axis is oriented along the y-axis can be described by a 4x4 matrix known as the Mueller matrix,
  • the measurement of the Mueller matrix members m 42 and m 43 is done by illuminating
  • circular analyzer which is composed of a QWP oriented at 0° and a polarizer oriented
  • I" 5 ( /f 45 ) are denoted by I" 5 ( /f 45 ), were a equals 0° or 45° for horizontally or 45° oriented

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Facsimile Transmission Control (AREA)
  • Storage Device Security (AREA)
  • Polarising Elements (AREA)

Abstract

L'invention concerne un procédé est un dispositif de chiffrage et de déchiffrage de données d'entrée. Le procédé de chiffrage consiste à produire un support pour les données sous la forme d'un élément réseau de sous-longueurs d'ondes variable à espace variant, les réseaux locaux présentant des angles d'orientation correspondant aux données.
PCT/IL2005/000675 2004-06-25 2005-06-23 Chiffrage et dechiffrage de donnees de phase geometrique Ceased WO2006001012A2 (fr)

Applications Claiming Priority (2)

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US58243904P 2004-06-25 2004-06-25
US60/582,439 2004-06-25

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WO2006001012A2 true WO2006001012A2 (fr) 2006-01-05
WO2006001012A3 WO2006001012A3 (fr) 2009-04-23

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI405448B (zh) * 2006-04-18 2013-08-11 Ibm 儲存系統中之資料加密
CN104159073A (zh) * 2014-07-21 2014-11-19 中国人民武装警察部队工程大学 一种基于双随机相位编码的视频光学加解密系统及方法
CN115327677A (zh) * 2022-04-14 2022-11-11 西北工业大学 一种实现偏振信息加密的矢量超表面及设计方法

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4892385A (en) * 1981-02-19 1990-01-09 General Electric Company Sheet-material authenticated item with reflective-diffractive authenticating device
US6314220B1 (en) * 1995-03-13 2001-11-06 Templex Technology, Inc. Segmented complex fiber gratings
US5680588A (en) * 1995-06-06 1997-10-21 International Business Machines Corporation Method and system for optimizing illumination in an optical photolithography projection imaging system

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI405448B (zh) * 2006-04-18 2013-08-11 Ibm 儲存系統中之資料加密
CN104159073A (zh) * 2014-07-21 2014-11-19 中国人民武装警察部队工程大学 一种基于双随机相位编码的视频光学加解密系统及方法
CN115327677A (zh) * 2022-04-14 2022-11-11 西北工业大学 一种实现偏振信息加密的矢量超表面及设计方法
CN115327677B (zh) * 2022-04-14 2024-01-30 西北工业大学 一种实现偏振信息加密的矢量超表面及设计方法

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WO2006001012A3 (fr) 2009-04-23

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