This paper describes about a Image steganography technique to hide information into a cover page based on Block-DCT, and Huffman coding. Huffman encoding is on the secret messages/images before embedding and each bit of secret message/image is embedded in the frequency domain by modifying the least significant bit of cover image blocks DCT coefficients. This algorithm has a good invisibility and capacity. Peak signal to Noise Radio of cover image with stego-image gives better results when compared to that of existing steganography approaches. The secret message/image cannot be extracted without knowing Huffman table and decoding rules.
Image Steganography Algorithm:
The main objective of Steganography is the true message cannot able to observe by an observer. Unauthorized users are not supports to differentiate a cover-image i.e., an image does not contain an secret message and stego-mage i.e., cover-image is modified and results a stego-image with secret message. Now-a-days steganograhpy is widely used in computer where digital data acts as carriers and networks acts as speed delivery channels.
Image steganography schemes are classified spatial-domain based category and transform-domain based category. In spatial domain approaches, the embedding of secret messages takes place directly. The simplest stegonographic method in spatial domain is Least Significant Bits Insertion method. Secret image is encoded using Huffman coding and then the secret image is embedded into cover image. Huffman codes are optimal codes in which one symbol maps to one code word.
In spatial domain, a steganography process improved security and image quality, compared to that of existing algorithms. It is very difficult to differentiate original image with the steganography algorithm resultant stego-image. This algorithm also provides 3 layers of security to cover image transformation. But the demand for image robustness in steganography is not as much as in watermarking field. Image in steganography process neglects the basic demand of robustness. This algorithm performs few operations and Huffman encoding of secret image helps to protect the images from stealing or misuse by unintended users.
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