Steganography is a technique which is used for securing the secret information from the illegal activity. Steganalysis is technique of finding the hidden text from the stego image. A Steganalysis based on the DCT value of the image is proposed in this paper. Steganography F5 algorithm is greater secure than other Algorithm. In this paper, we present a steganalytic method that can reliably detect messages (and estimate their size) hidden in JPEG images using the steganographic algorithm F5. The key element of the method is estimation of the cover-image histogram from the stego-image. This is done by decompressing the stego-image, cropping it by four pixels in both directions to remove the quantization in the frequency domain, and recompressing it using the same quality factor as the stego-image. The number of relative changes introduced by F5 is determined using the least square fit by comparing the estimated histograms of selected DCT coefficients with those of the stegoimage. Experimental results indicate that relative modifications as small as 10% of the usable DCT coefficients can be reliably detected. The method is tested on a diverse set of test images that include both raw and processed images in the JPEG and BMP formats. F5 implements matrix encoding to improve the efficiency of embedding. Thus it reduces the number of necessary changes. F5 employs permutative straddling to uniformly spread out the changes over the whole steganogram. In this paper, we also introduce to compress the size of the message or a doc file within an image, audio or a video.

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