Visual Cryptography
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The document discusses visual cryptography, which is a cryptographic scheme that enables the secure encoding and decoding of images without complex computations. It highlights the historical evolution of cryptography, including early methods like hieroglyphics and the Caesar cipher, and details the process of visual cryptography involving shares of pixels. Future developments in the field aim to enhance applications by improving image quality and allowing for implementation with color images.
Visual Cryptography
- 1. VISUAL CRYPTOGRAPHY Dr. Qaim Mehdi Department of Computer Science
- 2. What is Cryptography? Cryptography is the science of information security. The main objective of cryptography is information hiding.
- 3. What is Cryptography? Cryptography is the science of information security. The main objective of cryptography is information hiding.
- 4. History of Cryptography-1: Hieroglyphics Cryptography probably began in or around 2000 BC in Egypt, where hieroglyphics were used to decorate the tombs of deceased rulers and kings. COMPUTER SCIENCE COMPUTER SCIENCE
- 5. History of Cryptography-2: Wax Tablet A wax tablet is a tablet made of wood and covered with a layer of wax. It was used as a reusable and portable writing surface in the 1400 BC.
- 6. History of Cryptography-3: Caesar Cipher The first known use of a modern cipher was introduced by Julius Caesar (100 BC to 44 BC), who did not trust his messengers when communicating with his governors. Failure is success if we learn from it. Idloxuh lv vxffhvv li zh ohcuq iurp lw.
- 7. Visual Cryptography It is a new type of cryptographic scheme, which can decode concealed images without any cryptographic computations. The scheme is perfectly secure and very easy to implement.
- 8. Visual Cryptography It is a new type of cryptographic scheme, which can decode concealed images without any cryptographic computations. The scheme is perfectly secure and very easy to implement. Adi Shamir is a cryptographer and co-inventor of the famous RSA algorithm. Moni Naor is a computer scientist and also famous for his Turing Test on verification of a human in the loop.
- 9. Pixel Pixel is the smallest addressable element in a picture element.
- 10. Grayscale-level Grayscale Level is the brightness value assigned to a pixel; values range from black, through gray, to white.
- 11. Qualified Participants A qualified set of participants is a subset of Ρ whose shares visually reveal the 'secret' image when stacked together. Qualified Participant Qualified Participant Forbidden Participant
- 12. Qualified Participants A forbidden set of participants is a subset of Ρ whose shares reveal absolutely no information about the 'secret' image when stacked together. Forbidden Participant Qualified Participant Qualified Participant
- 13. Visual Cryptography: The Objective Encrypting written material (printed text, handwritten notes, pictures, etc.) in a perfectly secure way which can be decoded directly by the human visual system.
- 14. Visual Cryptography: The Approach The message consists of a collection of black and white pixels and each pixel is handled separately. Each original pixel appears in n modified versions (called shares), one for each transparency.
- 15. Visual Cryptography: The Approach The message consists of a collection of black and white pixels and each pixel is handled separately. Each original pixel appears in n modified versions (called shares), one for each transparency. Horizontal Share Vertical Share Diagonal Share
- 16. Visual Cryptography: The Process Continue… Original Pixel Share 1 Share 2 Overlaid
- 17. Visual Cryptography: The Process Original Pixel Share 1 Share 2 Overlaid 1 0 0 1 0 1 0 1 0 11 1 0 Continue…
- 18. Illustration of Visual Cryptography Pixel (0) Pixel (1)
- 19. Illustration of Visual Cryptography m sub-pixels m sub-pixels n shares pixel or or Example. n = 2, m = 4 Continue…
- 20. Illustration of Visual Cryptography horizontal shares vertical shares diagonal shares Secret Message Continue…
- 21. Illustration of Visual Cryptography horizontal shares vertical shares diagonal shares Continue…
- 24. Future Scope We can improve result by removing digital noise(gray-shades). With some minor changes, we can implement visual cryptography on color images.
- 25. References M. Naor and A. Shamir, Visual cryptography, in "Advances in Cryptology { EUROCRYPT '94", A. De Santis, ed., Lecture Notes in Computer Science 950 (1995), 1-12. G. Ateniese, C. Blundo, A. De Santis and D. R. Stinson, Visual cryptography for general access structures, Information and Computation 129 (1996), 86-106. C. Blundo, A. Giorgia Gaggia and D. R. Stinson, On the dealer's randomness required in secret sharing schemes, Designs, Codes and Cryptography 11 (1997), 107-122. W. Hawkes, A. Yasinsac, C. Cline, An Application of Visual Cryptography to Financial Documents, technical report TR001001, Florida State University (2000). Nakajima, M. and Yamaguchi, Y., Extended Visual Cryptography for Natural Images, WSCG02 (2002), 303. D Chaum, Secret-ballot receipts: True voter-veriable elections, IEEE Security and Privacy (2004), 38-47. A.Klein, M. Wessler, Extended Visual Crypotography Schemes, Science Direct (2007), 716-732. A. Bonis and A.Santis, Randomness in secret sharing and visual cryptography schemes, Theoretical Comp. Sci. 314 (2004), 351-374.
- 26. Thanks
- 27. Queries