EC-Council: Computer Hacking Forensic Investigator(CHFI-V10) |
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Module 3 : Understanding Hard Disks and File Systems |
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Note ID: 159
Analysis of Image formats with hex editors
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JPEG-The JPEG (Joint Photographic Experts Group) is a commonly used method to compress photographic images. It uses a compression algorithm to minimize the size of a file without affecting the quality of the image. Header ffd8 and footer ffd9.
BMP- The Bitmap (BMP) is a standard file format for a Windows Device Independent Bitmap (DIB) file The size and color of these images can vary from 1 bit per pixel (black and white) to 24-bit color (16.7 million colors).Every bitmap file contains the following data structures:
▪ File header: The first part of a bitmap file is the header, which includes data about the type, size, and layout of the file
▪ Information header: It is a header component that contains the dimensions, compression type, and color format of the bitmap ▪ Image data: It is an array of bytes that contains bitmap image data; image data comprises color and shading information for each pixel.
A bitmap file always has 42 4D as the first characters in hexadecimal representation.
GIF- The GIF is a file format that contains 8 bits per pixel and displays 256 colors per frame It uses a lossless data compression technique to maintain the visual quality of the image. Signature header- 47 49 46 38
PNG- The PNG is a lossless data compression image format, intended to replace the GIF and TIFF formats.
It supports the following: Indexed/Palette-based images (24-bit RGB or 32-bit RGBA colors) Grayscale images (with or without alpha channel) Transparency (both normal and alpha channel).Signature header- 89 50 4e 47  |
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