technique for image encryption using digital signature

We propose a new technique to encrypt an image for secure image transmission. The digital signature of the original image is added to the encoded version of the original image. The encoding of the image is done using an appropriate error control code, such as a Bose-Chaudhuri Hochquenghem (BCH) code. At the receiver end, after the decryption of the image, the digital signature can be used to verify the authenticity of the image. Detailed simulations have been carried out to test the encryption technique. An optical correlator, in either the JTC or the VanderLugt geometry, or a digital correlation technique, can be used to verify the authenticity of the decrypted image.

Information security is becoming more and more important with the progress in the exchange of data for electronic commerce. Images have considerable utility in our daily life. They are the basis of most security verification systems and are widely used for the identification of people, verification of cards, and other identities. Thus, reliable image encryption techniques are of utmost importance for the protection of data from counterfeiting, tampering, and unauthorized access [ 1- 12]. These image encryption techniques employ a kind of randomness, which cannot be inferred by other unauthorized users. A primary image encryption technique involves a process in which a primary image is encoded with two random phase masks. One mask is placed in the input plane and the other one in the spatial frequency plane. This results in the formation of a stationary white noise. In the decoding process, the encoded or the encrypted image is Fourier transformed, then multiplied by the complex conjugate of the random phase mask, and finally inverse Fourier transformed. This is known as the double random phase encoding system [1,2]. Optical implementations of the double random phase encoding system have also been reported. The encrypted image is recorded as a hologram by using a reference beam and the decryption of the image is done by using the phase conjugate of the random phase mask.

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