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Stego-SIRDS

Learn how to embed hidden data in a 24-bit image file using LSB manipulation and a selection function to achieve high fill factors. Discover the effectiveness of different fill levels in concealing data and creating stereo images.

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Stego-SIRDS

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  1. Stego-SIRDS William L. Bahn CS-591 Project 07 December 2005

  2. A Common Steganographic Technique • Use a 24-bit image file • Strip 1 or 2 LSB’s from each byte • Replace with the Stego-data

  3. How to embed the buried data? • As part of the fundamental image. • Use data source as random number source. • Mark non-random pixels. • Between 20% and 75% of pixels are random. • Fill factors of up to 60% to 70% achievable. • Full pixel replacement • Use some agreed upon selection function. • Fill factors of 25% to 33% achievable. • The typical way – LSB replacement. • Random data – fill factors of 87.5% achievable. • Raw data – fill factors of 50% to 75% achievable.

  4. 2-bit Stego-Image (25% fill factor)(taken from Wikipedia)

  5. Normal image at 50% fill Unmodified Cover Image Stego-image w / 50% fill

  6. Normal image at 75% reverse fill Unmodified Cover Image Stego-image w / 75% rev fill

  7. Unmodified SIRDS image

  8. Strong stereo image even with only the most significant bit retained! Unmodified Cover Image Stego-image w / 87.5% fill

  9. BUT…. • Prior image used pseudorandom buried data. • Use of encryption/compression can randomize data. • Random buried data can sometime ease analysis. • But this is not the case here - the “R’ in SIRDS!

  10. Even side by side it isn’t too obvious Unmodified Cover Image Stego-image w / 50% fill

  11. So what does it hide? Stego-image w / 50% fill My house!

  12. 87.5% fill is a waste of time Unmodified Cover Image Stego-image w / 87.5% fill

  13. 75% fill has obvious artifacts - very difficult to view stereo-image Unmodified Cover Image Stego-image w / 75% fill

  14. 75% reverse fill shows minor artifacts but is viewable as a stereo image Unmodified Cover Image Stego-image w / 75% rev fill

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