Improvements in secret image sharing schemes and the design of a new geometry based technique

Secret image sharing problems are investigated in this thesis and new schemes are proposed to overcome these. Proposed schemes are designed to deal with problems such as improving PSNR of shares, increasing number of authentication bits without degrading share quality, reducing cover image size to hide shares, recovering cover images after the reconstruction of secret image and make use of adaptive authentication depending on both cover and secret images. A new secret image sharing scheme for medical images is also considered and developed. Proposed medical image sharing scheme not only deals with security of secret image but also handles electronic patient record and introduces trust mechanism to a group of shareholders different from similar studies reported in the literature. Another secret image sharing scheme based on the Morley?s triangle theorem is proposed to recover the secret image even if shares are distorted.Results are compared with similar studies reported in the literature to reveal the strengths of proposed secret image sharing schemes.