## Pure optical dynamical color encryption |

Optics Express, Vol. 19, Issue 15, pp. 13779-13786 (2011)

http://dx.doi.org/10.1364/OE.19.013779

Acrobat PDF (1273 KB)

### Abstract

We introduce a way to encrypt-decrypt a color dynamical phenomenon using a pure optical alternative. We split the three basic chromatic channels composing the input, and then each channel is processed through a 4f encoding method and a theta modulation applied to the each encrypted frame in every channel. All frames for a single channel are multiplexed. The same phase mask is used to encode all the information. Unlike the usual procedure we do not multiplex the three chromatic channels into a single encoding media, because we want to decrypt the information in real time. Then, we send to the decoding station the phase mask and the three packages each one containing the multiplexing of a single channel. The end user synchronizes and decodes the information contained in the separate channels. Finally, the decoding information is conveyed together to bring the decoded dynamical color phenomenon in real-time. We present material that supports our concepts.

© 2011 OSA

## 1. Introduction

1. F. Mosso, J. F. Barrera, M. Tebaldi, N. Bolognini, and R. Torroba, “All-optical encrypted movie,” Opt. Express **19**(6), 5706–5712 (2011). [PubMed]

1. F. Mosso, J. F. Barrera, M. Tebaldi, N. Bolognini, and R. Torroba, “All-optical encrypted movie,” Opt. Express **19**(6), 5706–5712 (2011). [PubMed]

7. L. Chen and D. Zhao, “Optical color image encryption by wavelength multiplexing and lensless Fresnel transform holograms,” Opt. Express **14**(19), 8552–8560 (2006). [CrossRef] [PubMed]

9. M. Joshi, Chandrashakher, and K. Singh, “Color image encryption and decryption using fractional Fourier transform,” Opt. Commun. **279**(1), 35–42 (2007). [CrossRef]

10. D. Amaya, M. Tebaldi, R. Torroba, and N. Bolognini, “Digital color encryption using a multi-wavelength approach and a joint transform correlator,” J. Opt. A, Pure Appl. Opt. **10**(10), 104031 (2008). [CrossRef]

12. M. Tebaldi, S. Horrillo, E. E. Pérez-Cabré, M. S. Millán, D. Amaya, R. Torroba, and N. Bolognini, “Experimental color encryption in a joint transform correlator architecture,” J. Phys.: Conf. Ser. **274**, 012054 (2011). [CrossRef]

## 2. Procedure description

1. F. Mosso, J. F. Barrera, M. Tebaldi, N. Bolognini, and R. Torroba, “All-optical encrypted movie,” Opt. Express **19**(6), 5706–5712 (2011). [PubMed]

*f*double random phase encoding architecture [6

6. D. Amaya, M. Tebaldi, R. Torroba, and N. Bolognini, “Multichanneled puzzle-like encryption,” Opt. Commun. **281**(13), 3434–3439 (2008). [CrossRef]

*f*decrypting architecture. The entire procedure leads to clearly visualize each single frame without the influence of the others.

_{i}is multiplied by a sinusoidal grating G

_{i}of pitch d

_{i}which fulfills

*n*frames in the same medium. In Fig. 2 we include the filtering, synchronization and decryption steps that allow obtaining the final composed decrypted movie. In the same way the mathematical formulations associated to each one of these steps are included. In this way, we introduce for the first time a color crypto movie based on a whole optical approach.

_{i}gives rise to three terms one centered in the optical axis and the other two symmetrically located around the centered term. The location of these spots depends on the grating orientation and pitch and the size depends on the parameters of the optical system. We are storing

*n*frames; therefore we are obtaining several diffracted spots. The filtering procedure F is performed on the Fourier plane, by adequately positioning a circle of unitary transmittance scaled to the size of the diffracted order while assigning zero transmittance to the rest. By adequately selecting the filter position, we retain from the i-th term of Eq. (1) only one diffracted spot associated to

*f*scheme. At this step, the conventional decrypting procedure allows recovering the frame

*n*times in order to decrypt all movie frames for each color channel.

*f*single encrypting-decrypting procedure. In this way, we observe the behavior depicted in Fig. 5(a) where we plot the NRMS for the three wavelengths thus obtaining values between 0.05 and 0.1, showing that there is no appreciable difference between the corresponding outputs. In Figs. 5 b) an c), we include the image of frame number 25

^{th}extracted from the multiplexing operation and the corresponding single decrypted frame for simple visual comparison. It is important to remark the ever present noise aspect on all decrypted images where a speckle phase mask is used as encoding key.

*f*encrypting procedure. Multiplexing encryption arrangements are immune to known attack procedures (chosen plain text, known plain text, brute force, blind) that rely on the existence of an input-encrypted image pair. In this sense, multiplexing actions increase the protection against intruders.

## 3. Conclusions

## Acknowledgments

## References and links

1. | F. Mosso, J. F. Barrera, M. Tebaldi, N. Bolognini, and R. Torroba, “All-optical encrypted movie,” Opt. Express |

2. | P. Refregier and B. Javidi, “Optical image encryption based on input plane and Fourier plane random encoding,” Opt. Lett. |

3. | J. Barrera, R. Henao, M. Tebaldi, R. Torroba, and N. Bolognini, “Multiple image encryption using an aperture-modulated optical system,” Opt. Commun. |

4. | J. Fredybarrera, R. Henao, M. Tebaldi, R. Torroba, and N. Bolognini, “Multiplexing encryption-decryption via lateral shifting of a random phase mask,” Opt. Commun. |

5. | J. Barrera, R. Henao, M. Tebaldi, R. Torroba, and N. Bolognini, “Multiplexing encrypted data by using polarized light,” Opt. Commun. |

6. | D. Amaya, M. Tebaldi, R. Torroba, and N. Bolognini, “Multichanneled puzzle-like encryption,” Opt. Commun. |

7. | L. Chen and D. Zhao, “Optical color image encryption by wavelength multiplexing and lensless Fresnel transform holograms,” Opt. Express |

8. | L. Chen and D. Zhao, “Color information processing (coding and synthesis) with fractional Fourier transforms and digital holography,” Opt. Express |

9. | M. Joshi, Chandrashakher, and K. Singh, “Color image encryption and decryption using fractional Fourier transform,” Opt. Commun. |

10. | D. Amaya, M. Tebaldi, R. Torroba, and N. Bolognini, “Digital color encryption using a multi-wavelength approach and a joint transform correlator,” J. Opt. A, Pure Appl. Opt. |

11. | D. Amaya, M. Tebaldi, R. Torroba, and N. Bolognini, “Wavelength multiplexing encryption using joint transform correlator architecture,” Appl. Opt. |

12. | M. Tebaldi, S. Horrillo, E. E. Pérez-Cabré, M. S. Millán, D. Amaya, R. Torroba, and N. Bolognini, “Experimental color encryption in a joint transform correlator architecture,” J. Phys.: Conf. Ser. |

13. | A. Carnicer, M. Montes-Usategui, S. Arcos, and I. Juvells, “Vulnerability to chosen-cyphertext attacks of optical encryption schemes based on double random phase keys,” Opt. Lett. |

14. | X. Peng, P. Zhang, H. Wei, and B. Yu, “Known-plaintext attack on optical encryption based on double random phase keys,” Opt. Lett. |

**OCIS Codes**

(030.6140) Coherence and statistical optics : Speckle

(070.4560) Fourier optics and signal processing : Data processing by optical means

(060.4785) Fiber optics and optical communications : Optical security and encryption

**ToC Category:**

Image Processing

**History**

Original Manuscript: April 12, 2011

Revised Manuscript: June 19, 2011

Manuscript Accepted: June 21, 2011

Published: July 5, 2011

**Citation**

Fabian Mosso, Myrian Tebaldi, John Fredy Barrera, Néstor Bolognini, and Roberto Torroba, "Pure optical dynamical color encryption," Opt. Express **19**, 13779-13786 (2011)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-15-13779

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### References

- F. Mosso, J. F. Barrera, M. Tebaldi, N. Bolognini, and R. Torroba, “All-optical encrypted movie,” Opt. Express 19(6), 5706–5712 (2011). [PubMed]
- P. Refregier and B. Javidi, “Optical image encryption based on input plane and Fourier plane random encoding,” Opt. Lett. 20(7), 767–769 (1995). [CrossRef] [PubMed]
- J. Barrera, R. Henao, M. Tebaldi, R. Torroba, and N. Bolognini, “Multiple image encryption using an aperture-modulated optical system,” Opt. Commun. 261(1), 29–33 (2006). [CrossRef]
- J. Fredybarrera, R. Henao, M. Tebaldi, R. Torroba, and N. Bolognini, “Multiplexing encryption-decryption via lateral shifting of a random phase mask,” Opt. Commun. 259(2), 532–536 (2006). [CrossRef]
- J. Barrera, R. Henao, M. Tebaldi, R. Torroba, and N. Bolognini, “Multiplexing encrypted data by using polarized light,” Opt. Commun. 260(1), 109–112 (2006). [CrossRef]
- D. Amaya, M. Tebaldi, R. Torroba, and N. Bolognini, “Multichanneled puzzle-like encryption,” Opt. Commun. 281(13), 3434–3439 (2008). [CrossRef]
- L. Chen and D. Zhao, “Optical color image encryption by wavelength multiplexing and lensless Fresnel transform holograms,” Opt. Express 14(19), 8552–8560 (2006). [CrossRef] [PubMed]
- L. Chen and D. Zhao, “Color information processing (coding and synthesis) with fractional Fourier transforms and digital holography,” Opt. Express 15(24), 16080–16089 (2007). [CrossRef] [PubMed]
- M. Joshi, Chandrashakher, and K. Singh, “Color image encryption and decryption using fractional Fourier transform,” Opt. Commun. 279(1), 35–42 (2007). [CrossRef]
- D. Amaya, M. Tebaldi, R. Torroba, and N. Bolognini, “Digital color encryption using a multi-wavelength approach and a joint transform correlator,” J. Opt. A, Pure Appl. Opt. 10(10), 104031 (2008). [CrossRef]
- D. Amaya, M. Tebaldi, R. Torroba, and N. Bolognini, “Wavelength multiplexing encryption using joint transform correlator architecture,” Appl. Opt. 48(11), 2099–2104 (2009). [CrossRef] [PubMed]
- M. Tebaldi, S. Horrillo, E. E. Pérez-Cabré, M. S. Millán, D. Amaya, R. Torroba, and N. Bolognini, “Experimental color encryption in a joint transform correlator architecture,” J. Phys.: Conf. Ser. 274, 012054 (2011). [CrossRef]
- A. Carnicer, M. Montes-Usategui, S. Arcos, and I. Juvells, “Vulnerability to chosen-cyphertext attacks of optical encryption schemes based on double random phase keys,” Opt. Lett. 30(13), 1644–1646 (2005). [CrossRef] [PubMed]
- X. Peng, P. Zhang, H. Wei, and B. Yu, “Known-plaintext attack on optical encryption based on double random phase keys,” Opt. Lett. 31(8), 1044–1046 (2006). [CrossRef] [PubMed]

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