n-out-of-n Digital Image Sharing Scheme Based on Color Palette

• Main Authors: Chi-Ming Wu, 吳啟銘
• Other Authors: Ching-Nung Yang
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/pv3ezd

碩士 === 國立東華大學 === 資訊工程學系 === 107 === Sharing digital image by secret sharing technology is an important research area combining cryptography and image processing. In 1979, Shamir published a landmark paper that a (k, n)-Secret Sharing (SS) hiding a secret data by using a (k1)-degree polynomial. A combination of secret sharing and image processing has the threshold property of sharing image may achieve more applications. In a (k, n) secret image sharing (SIS), a secret image is shared into n shadow images. Any k shadow images may reveal the secret image, while less than k shadow images have no information about the secret image. The so-called (2, 2) sharing digital image scheme (SDIS) (referred to as (2, 2)-SDIS) adopts a color palette to share a digital color secret image into two shadow images. A (2, 2)-SDIS is just another type of (k, n)-SIS where k=n=2. When using col-or-palette image, we can substantially decrease the storage size of shadows and more effectively transmit via Internet. Up to date, the researches about SDIS is only (2, 2) scheme. In this thesis, we extend (2, 2)-SDIS to (n, n)-SDIS, where n>=3. Our (n, n)-SDIS scheme is designed based on (2, 2)-SDIS. However, we use 5 black 4 white (5B4W) block to 6B3W block, to represent the color index of 0~255. Via increasing the number of black pixels, our (n, n)-SDIS scheme has higher resolution of shadow images, i.e., the black and white pixels in block demonstrate the higher contrast of binary meaningful shadow images, as well as the higher resolution of colorful meaningful shadow images. Our scheme can also be applied on sharing true-color secret image. In addition, we also propose a scheme to improve the resolution of shadow images further. When changing 5B4W block to 6B3W block, how to obtain the color index 0~255 from XOR-ing two blocks, we design a novel approach based on previous (2, 2) schemes. In this thesis, we also theoretically prove that our (n, n)-SDIS is secure, resistant to (n-1)-colluder attack theoretically, and has better performance than previous (2, 2)-SDIS schemes.