The ringed shadow image technology of visual cryptography by applying diverse rotating angles to hide the secret sharing

摘要

The visual cryptography, which differs from conventional visual cryptography that is restricted to four specific angles (0/spl deg/, 90/spl deg/, 180/spl deg/, 270/spl deg/) , can hide two sets of confidential data into the ringed shadow images and present them by applying diverse rotating angles. Due to the purpose of reaching arbitrary rotating angles, we have presented a new coding measure to demonstrate two sets of confidential data from the correspondent two ringed shadow images via rotating angle easily. This angle is located among the entire 360/spl deg/ circles arbitrarily. The measure raised in this thesis has not only overwritten the angle restriction of conventional visual cryptography, it also has made a significant modification on the method of displaying the two sets of data embedding in the encrypted imagines. The preceded study relevant to this topic is to present diverse confidential data by using various areas, which makes a serious degradation of resolution for partial encrypted images in regard of the area's location. Therefore, this thesis of study finds a way to present a clear and complete confidential data regardless the area is located at.