Image encryption techniques based on the fractional Fourier transform

B. M. Hennelly; J. T. Sheridan

doi:10.1117/12.509137

23 October 2003 Image encryption techniques based on the fractional Fourier transform

B. M. Hennelly, J. T. Sheridan

Proceedings Volume 5202, Optical Information Systems; (2003) https://doi.org/10.1117/12.509137
Event: Optical Science and Technology, SPIE's 48th Annual Meeting, 2003, San Diego, California, United States

Abstract

The fractional Fourier transform, (FRT), is a generalisation of the Fourier transform which allows domains of mixed spatial frequency and spatial information to be examined. A number of method have recently been proposed in the literature for the encryption of two dimensional information using optical systems based on the FRT. Typically, these methods require random phase screen keys to decrypt the data, which must be stored at the receiver and must be carefully aligned with the received encrypted data. We have proposed a new technique based on a random shifting or Jigsaw transformation. This method does not require the use of phase keys. The image is encrypted by juxtaposition of sections of the image in various FRT domains. The new method has been compared numerically with existing methods and shows comparable or superior robustness to blind decryption. An optical implementation is also proposed and the sensitivity of the various encryption keys to blind decryption is quantified. We also present a second image encryption technique, which is based on a recently proposed method of optical phase retrieval using the optical FRT and one of its discrete counterparts. Numerical simulations of the new algorithm indicates that the sensitivity of the keys is much greater than any of the techniques currently available. In fact the sensitivity appears to be so high that optical implementation, based on existing optical signal processing technology, may be impossible. However, the technique has been shown to be a powerful method of 2-D image data encryption.

Citation Download Citation

B. M. Hennelly and J. T. Sheridan "Image encryption techniques based on the fractional Fourier transform", Proc. SPIE 5202, Optical Information Systems, (23 October 2003); https://doi.org/10.1117/12.509137

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