網點位移雙重加密應用於個人化郵票之研究

Abstract

本研究提出了一種以數位半色調及網點位移概念為基礎的雙重加密技術，此技術應用於個人化郵票設計可達到數位浮水印及資訊隱藏的複合效果，所製作之個人化郵票，不但可利用光學解碼透鏡，解出隱藏浮水印，另外可透過高解析掃描器掃瞄浮水印圖像部分，再配合影像處理程式解碼得到另一組隱藏資訊。本研究之高解析度加密浮水印影像，以彩色影印機無法複製浮水印，而達到防偽效果。且本研究解密方式可透過光學解碼透鏡（光柵）與電腦程式解密以得到不同隱藏資訊，進而達到多重防偽效果，也為個人化郵票添增趣味性及典藏價值，並更符合個人化產品的少量多樣化特性。

The double encryption basedon digital halftoning and dot shifting is stud-ied in this research. This double encryption technology can be applied to the design of personalized stamps with combined features of digital watermark and data hiding. The hidden watermark can be extracted by an optical decoder, and a part of stamp can be scanned through the high resolution scanner to get encrypted data. The stamp with hidden watermark in the study is output at 150LPI, and the watermark can’t be duplicated by the photocopier to achieve the anti-counterfeiting feature. In order to achieve multiple encryption and to make the personalized stamps more interesting, the hidden watermark and encrypt data can be decoded with the optical decoder and the computer pro-grams, respectively.