The Study Of Gray-image Steganography Based On Digital Audio

The information hiding technology mainly includes the steganography and digital watermark technology. The development of this technology, which is driven by secure communication and copyright protection, is very quickly in the past few years. The assurance of secure communication, especially the martial secure communication assurance is the most urgent. The traditional encryption techniques protect correspondence content and ensure the content not to be understood by the third party. Its basic method is scrambling. The steganography protects communication signals and ensures the signals not to be disturbed, detected and captured. Compared with the traditional encryption techniques, the steganography advances a lot. After enciphered, the information is always a heap of random codes. They are easy to draw attention and arouse the desire of decryption of illegal eavesdropper. Even though the illegal eavesdropper can not decrypt the secret information, successful intercepting could be very easy for them, even accurate destruction or disturbing the communication process. The aim of the steganography is to confuse the illegal eavesdropper not knowing where the secret information has. The steganography conceals the existent form of information. The untranslatability of codes depends on raising its key length continuously. However, with the rapid development of computing ability, the reliability of cipher faces new challenge and chances. Confronted with such circumstances, the steganography, which will not attract attention and arouse the desire of decryption of illegal eavesdropper, has attracted much attention of researchers.This paper, aiming at the steganography technology, mainly studies hiding algorithms that embedding a gray image, which considered as secret information, to the cover media (audio signal) for secret communication. The basic principle, background and current situation of steganography are introduced; the common technical terms are defined; and a specific classification of steganography system is given. Finally, the author presented and described three hiding methods, and discusses the security of each method detailedly as well.The major achievements of this paper are as follows: (1) For the sake of enhancing the security of steganography system, utilizing classical encryption techniques to encrypt the secret information before it is embedded into audio signal.Three kinds of encryption methods--Arnold scrambling, magic square scramblingand chaotic technique are introduced in detail. (2) In order to improve the anti-attack capability, the author chooses mid-frequency coefficients as the embedded position for the secret information embedding based on the discussion of steganography system objective requirement. (3)In order to improve the imperceptivity of the algorithm, this paper discusses the methods of embedding secret information in the DCT and DWT domain, and then introduces an improved method of adaptive steganography algorithm based on energy sorting. The algorithm makes good use of the masking effect of human audio system model and binds with the content of carrier digital audio signal, choosing the higher energy of audio segments as the secret-information-embedding digital audio segments. In this way, the imperceptibility and robustness are improved simultaneously.The experimental results show that DCT, DWT domain and improved algorithms can satisfy the imperceptibility and robustness when attacked by low pass filter, resample, lossy compression, noise adding and so on.