1 / 14

Digital Image Steganalysis

Digital Image Steganalysis. Kwang-Soo Lee. Outline. Steganography LSB Steganography LSB Steganalysis. Cryptography. Cryptography scrambles a message to obscure its meaning. Today secure communication is often identified with cryptography.

tayte
Download Presentation

Digital Image Steganalysis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Digital Image Steganalysis Kwang-Soo Lee

  2. Outline • Steganography • LSB Steganography • LSB Steganalysis

  3. Cryptography • Cryptography scrambles a message to obscure its meaning. • Today secure communication is often identified with cryptography. • However, cryptographyreveals the fact that communication is happening. ??? @2*$#d(*%7*

  4. Steganography • The word “steganography” comes from Greek, steganos and graphein. • Steganography is the art of hiding information in ordinary-looking objects. • Steganography aims to conceal the existence of secret communication.

  5. Classical Steganography • Examples: • Hidden tattoo, • Covered writing, • Invisible ink, • Microdots, • Character arrangement, • Paper mask, • etc. • Hiding a secret message in physical objects. • Secrecy depends on keeping the methods secret.

  6. Modern Steganography • Hiding information in digital objects, Invisibly. • The Invisibility must depend on just the stego-key, not the stego system.

  7. LSB Steganography • Replacing least-significant-bits (LSBs) of digital data with message bits. • Using digital multimedia, such as image, audio, video, as cover-objects. • Embedding random message bits in LSBs will not cause any discernable difference from the cover-signals. • Easy to implement, High payloads. Embedding 11001000 Extracting

  8. Digital Images for Steganography • Types of digital images: • binary, gray-scale, RGB color, palette, JPEG, etc. • The LSB plane of image data looks like random noise. • Bit-plane decomposition of the Lena image in gray-scale. lena.bmp 6th Bit Plane 4th Bit Plane LSB Plane

  9. LSB Steganalysis • Steganalysis is the science of detecting hidden messages in digital signals. • It takes advantage of statistical or perceptual distinction of stego-signals from cover-signals. • LSB steganalysis • Visual attack, • histogram analysis (PoV analysis), • Closed color analysis, • Regular-singular (RS) analysis, • Sample pair (SP) analysis, • LR Cube analysis, • Etc.

  10. PoV analysis • Proposed by Westfeld and Pfizmann (IH 1999) . • PoV means a pair of values which differ just in the LSBs. • 0 1 2 3 4 5 6 7 8 9 10 …… • LSB embedding tends to equalize those frequencies of the values of each PoV. LSB Embedding stego-image histogram cover-image histogram

  11. Sample Pair Analysis • Proposed by Dumitrescu et al. (IH 2003) • Based on symmetry of quantized noise distribution. • Take advantage of spatial correlation such as pixel adjacency. • Estimate the length of hidden message. • Outperform PoV analysis. LSB Embedding stego-image histogram cover-image histogram

  12. LR Cube Analysis • Left and Right cube analysis (LRCA), developed by us (IH 2005) • Our method uses high dim. vectors as basic units drawn from digital signals. • Consider the vector noise distribution and its distortion of LSB embedding.

  13. LR Cube Analysis • Left cube and Right cube, and the possible cube patterns or complexities. • Cover-signals show similar complex levels between the left cubes and the right cubes, but these are not the case for stego-signals after the LSB embedding • LRCA works by measuring the similarities between these two distributions.

  14. Thank youKwang-Soo Leekslee@cist.korea.ac.kr

More Related