Abstract
In this paper, a double-random phase-encoding technique-based text encryption and hiding method is proposed. First, the secret text is transformed into a 2-dimensional array and the higher bits of the elements in the transformed array are used to store the bit stream of the secret text, while the lower bits are filled with specific values. Then, the transformed array is encoded with double-random phase-encoding technique. Finally, the encoded array is superimposed on an expanded host image to obtain the image embedded with hidden data. The performance of the proposed technique, including the hiding capacity, the recovery accuracy of the secret text, and the quality of the image embedded with hidden data, is tested via analytical modeling and test data stream. Experimental results show that the secret text can be recovered either accurately or almost accurately, while maintaining the quality of the host image embedded with hidden data by properly selecting the method of transforming the secret text into an array and the superimposition coefficient. By using optical information processing techniques, the proposed method has been found to significantly improve the security of text information transmission, while ensuring hiding capacity at a prescribed level.
Highlights
In information security, cryptography, which encrypts the secret message before transmission to avoid information disclosure, is commonly used [1]
Since the recovery accuracy is defined as the ratio of the correctly recovered bytes, any text can be used as the secret text, while not influencing the experimental results significantly
Based on the number of higher bits of the elements in the transformed array A used for storing the bit stream of the secret text T, i.e., the value of m, the hiding capacities of the secret text will be different
Summary
Cryptography, which encrypts the secret message before transmission to avoid information disclosure, is commonly used [1]. The encryption methods are based on digital methods [1]. A typical optical image encryption method is the double-random phase-encoding (DRPE) technique, which encodes the original secret image to a complex-valued encoded image by applying independent random phase encoding on the input plane and the Fourier plane, respectively [2]. Thereafter, the DRPE-based optical image encryption method has been improved [3,4,5,6,7] and applied to other transformation domains, including optical encryption in the fractional Fourier domain [8,9,10,11,12], optical encryption in the Fresnel domain [13,14] and encrypting information with digital holography [15,16]. The encrypted secret message, i.e., the cyphertext, is usually unreadable
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