Advanced encypted blind watermarking hiding text
Abstract : Information security is a critical issue in modern society and image watermarking can effectively prevent unauthorized information access. Optical image watermarking techniques generally have advantages of parallel high-speed processing and multi-dimensional capabilities compared with digital approaches. This paper provides a comprehensive review on the research works related to optical image hiding and watermarking techniques conducted in the past decade. The past research works are focused on two major aspects, various optical systems for image hiding and the methods for embedding optical system output into a host image. A summary of the state-of-the-art works is made from these two perspectives.
? Encryption techniques transform the original image into noise-like ciphertext, which is not accessible by unauthorized users without the correct key.
? However, the existence of ciphertext is usually known to the third party. The aim of watermarking is to hide the existence of original image to unauthorized users.
? In this scheme, the crosstalk between different depth sections of the 3D object can yield a noise-like recorded diffraction patterns, which are favorable for watermarking applications.
? As a drawback, a large number of optical exposures, recorded diffraction patterns and host images are required.
? The problem of inconsistency in data representation format between gray scale image and phase-only image (or binary image) is addressed in these works with appropriate algorithms.
? With the rapid development of Internet and information technology, the problem of unauthorized acquisition, transmission, manipulation and distribution of digital content is increasingly more severe in recent years.
? This problem can be possibly tackled by combining these optical systems with some incoherent operations such as visual cryptography, where an approximate overlapping (rather than very precise alignment) of optical components can yield correct decrypted result.
• This paper presents a comprehensive review on various optical image watermarking systems and schemes proposed in the past decade.
• A method to detect whether there is DRPE encrypted secret information embedded in a given image is proposed.
• In, an image hiding technique is proposed that combines the complementary advantages of cascaded Fourier transform and RSA encryption algorithm, which is a hybrid of optical and digital security approaches.
• An improved single-shot-ptychography watermarking scheme is proposed by recording one diffraction intensity pattern constituting a series of tiny diffraction spots.
? These adaptive watermarking schemes can give more satisfactory watermarking performance (embedding more hidden ciphertext information into the host image while causing less damage to the host image) but the expense is much higher complexity.
? In, the hologram is weight added to the median-frequency coefficients of the discrete cosine transformed (DCT) host image instead of spatial domain.
? The low frequency and high frequency coefficients are well preserved so the host image quality after watermarking is better than the work.
? The wavelet coefficients are quantized by two different quantizers according to the binary bit values of the hidden holographic data.
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