結合圖像化二維條碼與微結構藏密之自我驗證研究

Abstract

科技發展改變了人們的生活習慣，透過網路應用讓線上與線下的整合發展日趨重要，二維條碼QR Code (Quick Response Code)，正可作為簡單且快速構連兩者間的媒介。條碼發展從線性（一維）到矩陣（二維），可儲存資料量與編碼內容隨之增加，搭配上智能行動裝置普及化，在生活中各種應用領域愈來愈多元，因此有許多學者投入二維條碼圖像化之研究，將傳統黑白方格呈現方式，在不影響讀取性、破壞程度最低方式植入個人化圖像，以提升條碼的美觀效果。即便如此，無法於掃描前預先辨識條碼資料來源真偽仍是現行使用上之缺點，如企圖變造條碼將不當資訊隱藏其中，使用者掃描後即有被竊取個資或財產損失之風險。 許多國家鈔券逐漸從纖維棉質紙張轉而朝向具有更耐用及防偽功能表現更佳之聚合物（Polymer）塑膠材質做應用，本研究鑒於圖像化二維條碼無法辨識資料來源真偽之安全風險及未來塑膠鈔券發展趨勢，參考現行鈔券凹版印刷線紋水平及垂直所造成之潛像概念，運用邏輯演算將圖像化二維條碼網點以左斜斜向線網呈現，並同時嵌入右斜線網之加密圖案，另外搭配光柵解碼片，以塑膠底片為基材運用其可透光特性進行輸出，不需要另備輔助儀器，於同一版面上透過彎曲覆蓋方式即可達到自我驗證真偽之效果。 針對本研究效果評估，確認微結構藏密條碼之數位影像判讀功能未被破壞，另為模擬人眼視覺效果將底紋與光柵透過高斯模糊方式進行調制轉換函數Mvalue值比較，採用150、300及600網線數進行輸出，搭配1-5pixels的光柵線幅寬度，經測試值評估，150線時解密效果最佳，其次依序為300線及600線，但由於150線底紋無法有效防止複印，本研究分析300線為兼具自我驗證並防止複印的網線數，搭配5 pixels之光柵線幅寬度為自我驗證之最佳組合，此結果可供未來有價證券上設計應用作為參考依據。

Technology development has changed people’s lives. With the application of internet, QR Code (Quick Response Code) becomes an interface connecting the physical and digital world. The barcode has developed from linear to two-dimensional format. This new matric format provides advantage for larger storage capabilities. Along with the popularity of smart phones, barcode applications are widely used nowadays. Thus, many researchers have dedicated their efforts to creating two-dimensional graphic barcodes through implanting personalized image from the traditional black and white barcode to improve the visual aesthetic without affecting its readability. However, the present graphic barcodes have its downside which cannot allow users to verify the authenticity of the information before scanning. This problem may compromise users' personal information or even cause financial loss. In addition, there are more and more countries begin to adopt polymer as the main component of producing banknotes due to its long lasting and anti-counterfeit functions. Based on the future trend of polymer currency notes and the existing 2D barcode security risk, this research utilizes a left-titling halftone screening to generate the graphic QR Code’s microstructure and embeds a hidden image by right-titling halftone screening simultaneously. A variety of lenticular lens with different line widths have also been outputted, applying plastic’s light transmitting characteristic, the self-authentication function can be achieved by simply covered with the substrate itself. For the evaluation of microstructure encrypted result, the graphic QR Code’s readability should be firstly examined and inserts the film of the resolution with the best self- authentication quality. For the evaluation of inspection effect that blurred the digital image to simulate human eyes, Gaussian Blur is applied to the microstructure and lenticular images with different line widths to compare the grayscale. A copy machine is utilized to further test the anti-counterfeit function and QR Code’s readability. This study utilizes 150, 300 and 600 lines per inch for shading output and 1-5 pixels of grating width. Through the digital image evaluation and copy test, 300 lines per inch output with 5 pixels grating width is the best parametric combination. The proposed method confirms that self-authentication technique is not only feasible but can also be used to help determine the suitable parameter for best decoding result before a formal outputting.