用於紅外線驗證之數位資訊加密系統 The Digital Information Encryption System by Infrared Detection

Date
2008
Authors
張家龍
Chia-Long Chang
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Abstract
本研究目的在提出以噴墨列印輸出建立的防偽機制,應用數位半色調和印墨材料在紅外線照射下的光學特性差異,構成具多重防偽功能的浮水印,與圖文整合時,經過編碼的隱藏資訊可接受一定程度的破壞,達到噴墨印刷品加值的效果。由於碳黑物質吸收紅外線,而青、洋紅、黃色墨在紅外線下可穿透而呈現透明,所以本研究利用此特性,將隱藏資訊的浮水印能藉由紅外線攝影裝置進行觀察和驗證。研究首先藉由臨界值矩陣產生的網點影像和不同階調之中性灰進行匹配實驗,輸出後找出目視距離下達到灰平衡的最適組合,將浮水設計成二維條碼的形式整合設計於身份證件的應用,之後利用紅外線攝影裝置觀察。編碼過程利用錯誤校正碼針對兩階浮水印影像進行容錯編碼,隱藏的浮水印資訊經由程式語言進行解密。結果顯示經目視觀察時,隱藏浮水印資訊呈現一致階調的影像,但透過紅外線攝影裝置觀察,可發現浮水印中碳黑墨形成的半色調影像呈現深色,中性灰則幾乎透明,視覺上即可看出顯著的對比,進而達到版權宣告的目的。浮水印可經由紅外線攝影裝置驗證,隱藏資訊遭攻擊時也能一定的容錯能力。
The objective of this research is to propose a method for inkjet printing to build anti-counterfeiting features by infrared detection. The multiple anti-counterfeiting watermark is constructed by digital halftoning techniques and the characteristics of ink materials. The method also provides many value-added applications for ink-jet printing process. Since carbon black absorbs infrared light, The research demonstrate that the latent information of watermark can be observed and verified under infrared light. The watermark is designed as a form of 2D barcode. The result that binary watermark has error correction capability by BCH error correction code. Digital halftoning technique and the threshold matrix are used to generate the watermarked printed image. The suitable image combination of gray patches by black and Cyan, Magenta and yellow patches are selected. The integrated design of an ID card is successfully implemented. The method achieve the purpose to declare copyright on the basis of the digital watermark. The results show that the watermark can be detected either by an infrared camera or by a copy machine and to withstand the noise attack.
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Keywords
防偽, 噴墨印刷, 數位半色調, 浮水印, 紅外線偵測, 二維條碼, anti-counterfeit, inkjet printing, digital halftone, watermark, infrared detection, 2D barcode
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