視覺密碼學的研究者一直以來的目標就是降低像素擴展與提升還原影像的品質。近年來提出的通用存取結構（General Access Structures），都是以像素擴展式機密分享的作法為主。Kafri與Keren 所提出的隨機網格，改善了像素擴展的問題。 本研究提出一個將機密影像依通用存取結構編碼為多張分享投影片，透過隨機編碼與控制分配的概念，產生相似於隨機網格的分享投影片，此模型具備漸進式還原效果的方法，我們稱之漸進式半隨機網格視覺機密分享模型（Progressive Semi-Random Grids Visual Secret Sharing Model；PSRD VSS Model），簡稱為PSRD模型。 The goal of visual cryptography''s researchers are reduce the pixel-expansion and enhance the restored image quality. General access structures that proposed in recent years based on pixel-expansion. Kafri and Keren （1987）proposed a random grid, to improve the pixel-expansion problems. This study proposes a general access structures of the secret image is encoded as multiple share transparencies, through the concept of random and control distribution, make the share transparencies that are similar to the random grid and restore with progressive, we call Progressive Semi-Random Grids Visual Secret Sharing Model referred to as PSRD VSS Model.
