Therefore, we can think of DCT as an approximate calculation method for performing compression. The number of bits required to display the image is reduced by identifying repeated pixels in adjacent pixels in each 8×8 pixel block, and the redundancy is reduced by using approximate estimation methods. The JPEG image format uses the Discrete Cosine Transform (DCT) function to compress images, and the core of this image compression method is: Part 1: Steganography of JPG pictures based on DCT domain
It is necessary to emphasize that steganography and cryptographic coding are completely different concepts. Steganography is written in English, and this content will take you to understand the common steganography of pictures on the CTF arena, and the solutions. Steganography is a technique and science about information hiding, that is, preventing anyone other than the recipient of the plan from knowing the transmission event of the information (not just the content of the information). This article is referenced from: Prophet Community: This should be the last article on steganography! ! MISC Summary-Steganography (3) For details, please see: MISC Summary-Steganography (2) For details, please see: MISC Summary-Steganography (1) For details, please see: This one is another one after the previous one about the common routine problems of steganography in ctf competitions:
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