The Study of Visually Sharing Secret Images
| Autor: | Chi-Cheng Liao, 廖基成 |
|---|---|
| Rok vydání: | 2009 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 97 Visual secret-sharing is a cryptography technique that uses an encryption method to encode secret image into several noise-like shared images with the purpose of protecting secret messages. The decryption phase involves stacking several shared images to get a reconstructed secret image in which the secret messages from the reconstructed secret image can be seen with the human eye. Traditional visual secret-sharing methods have had problems, including: (1) expansion problems with the reconstructed secret image, (2) reduced contrast of the reconstructed secret image because the image quality has been degraded, and (3) a shared image that is meaningless. In Chapter 2, we provide a meaningful shadow-based multiple gray-level (MSML) visual cryptography method without size expansion. This method creates a reconstructed secret image with multiple gray levels and without size expansion in which the created shadow images also appear similar to the cover images specified by the user. Moreover, a user can adjust the qualities of the reconstructed secret image and the shadow images according to his or her requirements. In Chapter 3, we provide a visual secret-sharing method for progressively restoring secrets. The benefits of the proposed method include (1) meaningful generated shadows whose sizes are not expanded and (2) a secret image that can be recovered at different resolutions by stacking different quantities of shadows together. The experimental results show that our proposed method is superior to other compared schemes. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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