Optical encryption interface

• US 5,793,871 A
• Filed: 11/26/1996
• Issued: 08/11/1998
• Est. Priority Date: 11/26/1996
• Status: Expired due to Term

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Jackson, Deborah J.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US08/756,993
• Time in Patent Office: 623 Days
• Field of Search: 380/9, 380/10, 380/28, 380/33, 380/43, 380/49, 380/54, 380/59, 380/6, 380/7, 380/8
• US Class Current: 380/54
• CPC Class Codes: H04K 1/006 by varying or inverting the phase, at periodic or random intervals

Abstract

An analog optical encryption system based on phase scrambling of two-dimensional optical images and holographic transformation for achieving large encryption keys and high encryption speed. An enciphering interface uses a spatial light modulator for converting a digital data stream into a two dimensional optical image. The optical image is further transformed into a hologram with a random phase distribution. The hologram is converted into digital form for transmission over a shared information channel. A respective deciphering interface at a receiver reverses the encrypting process by using a phase conjugate reconstruction of the phase scrambled hologram.

Claims

1. An encryption device operable to encrypt electronic data according to an algorithm, comprising:

a first electro-optical device, receiving electronic data and converting said electronic data into a two dimensional optical image

a second electro-optical device, disposed relative to said first electro-optical device and configured to receive an optical indicia of said optical image and to produce a two dimensional electrical signal array indicative of said optical image; and

an encryption device operable to cause said electrical signal array to be encrypted according to a key to form an encrypted electrical signal array.

2. A system as in claim 1, wherein said encryption device includes a phase modulating device, said phase modulating device operating to effect a phase modulation as said key in said electrical signal array produced by said second electro-optical device to form said encrypted electrical signal array.

3. A system as in claim 2, wherein said phase modulating device includes an optical element selected from a group at least consisting of a holographic medium, a phase spatial light modulator, and a multimode waveguiding medium.

4. A system as in claim 2, wherein said phase modulating device is an electronic device, operating to add said phase modulation to at least one of said first electro-optical device and said second electro-optical device.

5. A system as in claim 1, wherein said first electro-optical device is a spatial light modulator and said second electro-optical device is a two-dimensional light detector array.

6. A system as in claim 5, wherein said two dimensional light detector array is a CCD array.

7. A system as in claim 1, wherein said electrical signal array is indicative of an optical hologram having phase and intensity information of said optical image from said first electro-optical device.

8. A system as in claim 1, wherein said key is at least in part based on an algorithm selected from a group consisting of DES, RSA, Triple DES, REDOC, Khufu, and IDEA.

9. An information encryption system, comprising:

a first light source for producing a first signal light beam and a first reference light beam which are mutually coherent to each other;

a first electro-optical spatial light modulator having a two dimensional spatial array of pixels for modulating light and being disposed to receive said first signal light beam, said first light modulator operating to convert a first serial data stream into a first two-dimensional spatial pattern on said spatial array and to impress said first spatial pattern onto said first signal light beam to form a two dimensional optical image, wherein said first signal light beam impressed with said optical image and said first reference light beam are directed to overlap and interfere with each other to produce a first interference pattern according to a first predetermined relationship between said first signal light beam and said first reference light beam;

a first two-dimensional light detector array, disposed relative to said first light modulator to receive said first interference pattern and configured to convert said first interference pattern into a first electrical signal array; and

an encryption device operable to cause said first electrical signal array to be encrypted according to an encryption key to form a first encrypted electrical signal array, wherein said first encrypted electrical signal array is converted into an encrypted serial digital data stream.

10. A system as in claim 9, wherein said encryption device includes a first phase modulating device, producing a first phase modulation on one of said first signal light beam and said first reference light beam.

11. A system as in claim 10, wherein said first phase modulating device is located in the optical path of said first signal light beam between said first light modulator and said first detector array.

12. A system as in claim 10, wherein said first phase modulating device is disposed to modulate said first signal light beam prior to impressing said first spatial pattern onto said first signal light beam by said first light modulator.

13. A system as in claim 10, wherein said first phase modulating device is disposed to modulate said first reference light beam prior to said interference with said first signal light beam.

14. A system as in claim 10, wherein said first phase modulating device includes an element selected from a group at least consisting of a holographic medium, a phase spatial light modulator, and a multimode waveguiding medium.

15. A system as in claim 10, wherein said first phase modulating device is an electronic device electrically connected to one of said first light modulator and said first detector array and configured to add a random phase distribution to said first phase modulation.

16. A system as in claim 9, further comprising:

a second light source operable to produce a second signal light beam having a second predetermined relationship with said first reference beam; and

an optical decryption device operable to use said second signal beam to convert said encrypted serial digital data stream into a decrypted digital data stream substantially identical to said first digital data stream by performing an optical decryption process.

17. A system as in claim 16, wherein said optical decryption device includes:

a second electro-optical spatial light modulator disposed to receive said second signal light beam and configured to convert said encrypted serial data stream into a second two-dimensional interference pattern substantially identical to said first interference pattern, said second light modulator operable to impress said second interference pattern onto said second signal light beam.

18. A system as in claim 17, wherein:

said encryption device is configured to include a first phase modulator operating to produce a first phase modulation to one of said first signal light beam and said first reference light beam to effect said encryption of said first electrical signal array;

said optical decryption device is configured to include a second phase modulator to produce a second phase modulation associated with said first phase modulation to said second signal light beam, said second phase modulator being so positioned with respect to positioning of said first phase modulator relative to said first light modulator and said first detector array that said second phase modulator and said second light modulator operating in combination to produce a third beam having a second spatial pattern substantially identical to said first spatial pattern and propagating in a direction having a relation with respect to said first signal beam; and

is configured to further comprise;

a second two-dimensional detector array, disposed relative to said second light modulator to have a spatial relation therebetween substantially identical to a relative spatial positioning of said first detector array and said first light modulator, said second detector operating to receive said third signal beam and convert said second spatial pattern therein into said decrypted digital data stream.

19. A system as in claim 18, wherein both said second signal beam subsequent to said impressing by said second light modulator and said third beam retrace said first signal light beam in a time reversed manner.

20. A system as in claim 18, wherein said second phase modulator includes a holographic medium having a hologram therein that is associated with said first phase modulation by said first phase modulator.

21. A system as in claim 18, further comprising:

a first electronic device, electrically connected to said first spatial light modulator, operating to split said first serial digital data stream into a first portion and a second portion, said second portion being sent to said first spatial light modulator; and

a second electronic device, electrically connected to said first detector array, operating to combine said first portion of said first serial digital data stream and said encrypted serial digital data stream.

22. A system as in claim 16, wherein said second relationship of said second signal light beam with said first reference beam includes a property selected from a group at least consisting of propagating direction, wavelength, and polarization.

23. A system as in claim 9, wherein said first light source comprises a first light emitting device to produce said first signal light beam and a second light emitting device to produce said first reference light beam.

24. A system as in claim 9, wherein said first light source includes at least one diode laser.

25. A system as in claim 9, wherein said two dimensional light detector array is a CCD array.

26. A method of encrypting electronic data, comprising:

transforming a serial stream of data into a first two-dimensional spatial array of electrical signals;

using said first spatial array of electrical signals to modulate a wavefront of a signal beam to produce a modulated signal beam which carries a spatial image indicative of said first spatial array of electrical signals;

providing a reference light beam which is coherent with said signal beam and propagating relative to said modulated signal beam;

spatially overlapping said reference beam and said modulated signal beam according to a predetermined criterion to form interference fringes;

converting said interference fringes into a second two-dimensional spatial array of electrical signals;

encrypting said second spatial array of electrical signals by using a first key to form an encrypted second spatial array of electrical signals; and

transforming said encrypted second spatial array of electrical signals into a serial stream of encrypted data in time domain.

27. A method as in claim 26, wherein said first key includes a first phase modulation.

28. A method as in claim 27, wherein said first phase modulation is an optical phase modulation applied on said signal beam, thus resulting in said first phase modulation in said second spatial array of electrical signals.

29. A method as in claim 27, wherein said first phase modulation includes an optical phase modulation applied on said reference beam, thus resulting in presence of said first phase modulation in said second spatial array of electrical signals.

30. A method as in claim 27, wherein said first phase modulation includes an electronic phase modulation in said first spatial array of electrical signals to cause said first phase modulation in said second spatial array of electrical signals.

31. A method as in claim 27, wherein said first phase modulation includes an electronic phase modulation in said step of converting of said interference fringes into said second two-dimensional spatial array of electrical signals.

32. A method as in claim 27, further comprising:

transforming said encrypted data into a third two-dimensional spatial array of electrical signals that is substantially identical to said second spatial array of electrical signals;

modulating a read light beam with said third spatial array of electrical signals to generate a reconstruction beam whose wavefront is an optical indicia of said third spatial array of electrical signals;

converting said reconstruction beam into a fourth two-dimensional spatial array of electrical signals;

causing a second phase modulation in said fourth spatial array of electrical signals, wherein said second phase modulation has a phase relationship with said first phase modulation so as to substantially undo said first phase modulation; and

transforming said fourth spatial array of electrical signals into a serial stream of decrypted data in time domain that is substantially identical to said serial stream of data.

33. A method as in claim 32, wherein said read light beam counterpropagates said reference beam relative to said third spatial array of electrical signals with respect to propagation of said reference beam relative to said second spatial array of electrical signals and said reconstruction beam is substantially identical to the phase conjugate of said modulated signal beam.

34. A method as in claim 26, wherein said predetermined criterion includes wavelength, polarization, and relative propagating direction of said modulated signal beam and said reference beam.

35. A data transmission system based on optical encryption, comprising:

a transmission terminal having a first two dimensional spatial light modulator operable to convert electronic data into a first two dimensional optical image in a first read light beam and a first two dimensional light detector array operable to convert a first optical hologram of said first optical image into encrypted electronic data, wherein said encrypted electronic data is produced at least in part by effecting a first phase modulation in said first optical hologram; and

a receiving terminal having a second two dimensional spatial light modulator operable to convert said encrypted electronic data into a second two dimensional optical image in a second read light beam and a second two dimensional light detector array operable to convert said second optical image into said electronic data by applying a second phase modulation which removes said first phase modulation from said second optical image.

36. A system as in claim 35, further comprising a data communication channel connecting said transmission and receiving terminals to transmit said encrypted electronic data.

37. A system as in claim 36, wherein said data communication channel is connected to a communication network.

38. A system as in claim 37, wherein said data communication channel is connected to the Internet.

39. A system as in claim 35, wherein said first phase modulation is carried out electronically by said first spatial light modulator.

40. A system as in claim 35, wherein said first phase modulation is carried out electronically by said first light detector array.

41. A system as in claim 35, further comprising an optical phase scrambling medium in the optical path of said first read light beam to optically produce said first phase modulation.

42. A system as in claim 35, wherein said first optical hologram is formed by interfering a first reference beam with said first read light beam and further comprising an optical phase scrambling medium in the optical path of said first reference beam to optically produce said first phase modulation.

43. A system as in claim 41 or 42, wherein said optical phase scrambling medium is a holographic medium or a phase spatial light modulator.

44. A system in claim 41 or 42, wherein said optical phase scrambling medium is a multimode waveguiding medium which is operable to further add redundancy in said encrypted electronic data produced by said transmission terminal.

45. An encryption system operable to encrypt electronic data according to an algorithm, comprising:

a two dimensional spatial light modulator operable to convert electronic data into a two dimensional optical image in a read light beam; and

a two dimensional light detector array operable to convert a optical hologram of said optical image which is formed by interfering said read light beam with a reference beam into encrypted electronic data,

wherein said encrypted electronic data is produced by a first encryption based on a phase scrambling mechanism and a second encryption based on formation of said optical hologram.

46. A system as in claim 45, further comprising an optical phase scrambling device which is disposed to impress an optical phase modulation upon one of said read light beam and said reference beam to effect said first encryption.

47. A system as in claim 45, wherein said first encryption is a phase modulation that is electronically performed in one of said spatial light modulator and said light detector array.

48. A system as in claim 46 or claim 47, wherein said second encryption is based on at least one of propagating direction, wavelength, and polarization of said read light beam and said reference beam.