Watermarking for Layered Manufacturing

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Project title

Code/計畫編號

MOST109-2221-E019-055

Translated Name/計畫中文名

積層製造浮水印技術之研究

Project Coordinator/計畫主持人

Shyh-Kuang Ueng

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Computer Science and Engineering

Website

https://www.grb.gov.tw/search/planDetail?id=13535895

Year

2020

Start date/計畫起

01-08-2020

Expected Completion/計畫迄

31-07-2021

Bugetid/研究經費

671千元

ResearchField/研究領域

資訊科學--軟體

Layered Manufacturing (LM) is widely used in rapid prototyping, customized product design, and ad hoc manufacturing. However, models and G-code programs of LM processes are prolong to copyright violation, improper usage, and inappropriate production. In this research project, we will conduct a research aiming at the development of watermarking scheme dedicated for LM processes. The proposed scheme is an innovative one. The watermark is implicitly embedded in the G-code program used for fabricating the target model. It is impossible to remove the watermark unless the attackers do not want to produce the model. The verification process is accomplished by using volume rendering, virtual manufacturing, and physical 3D printing. It is easy to detect and verify the watermark. The resultant watermarking scheme of this research will be an effective method for (1) copyright protection, (2) product authentication, and (3) model and product classification. The proposed watermarking method includes the following steps: At first, the geometrical representation of the model is decomposed into a set of voxels. Then, a distance field is created upon the voxel-model. At the 3rd step, the user extracts an iso-surface from the distance field and specifies a region for watermarking. In the following computation, the watermark is embedded into the selected region by using texture mapping. Finally, the voxel-model is converted into a G-code program. To detect the watermark, a 3D printing simulator is employed to virtually manufacture the model by executing the G-code program. This process will produce a volume model which is a 3D image. The hidden watermark can be revealed by using volume rendering technique. Another way to verify the watermark is to compute the correlation between the detected and original watermarks and estimate the existence of the watermark by using statistic analysis. If a 3D printer is available, the user can also manufacture the physical product and verify the watermark visually. Compared with traditional watermarking methods, ours possesses the following advantages: (1) The watermark is implicitly embedded into the G-code program. Attackers cannot remove it without damaging the G-code program. (2) The watermark is texture-mapped inside the wall of the model. The outer appearance of the model is not altered. (3) Our watermarking scheme protects not only the model but also the G-code program. To our knowledge, there is no watermarking method available for protecting G-code programs from improper distribution or usage. (4) The proposed watermarking scheme can be used to carve the model to alter the shape, mechanic strength, and appearance of the final product. In conclusion, the resultant technology developed in this research project will benefit the manufacturing industries, medical applications, and knowledge protection processes. It will enhance the production capacity of our nation and encourage more people to contribute their energy and wisdom in invention, design, and manufacturing. 積層製造的設備成本低廉，而且能夠製造複雜結構的物體，所以它已經廣泛地被使用來從事客製化生產、產品設計、與零件製造。然而用來進行基層製造的模型與機器碼程式容易被模仿、盜用、或誤用，對設計者、生產者、與使用者都會造成財物損失或實體傷害。在本研究計畫，我們將研發一套專門應用於基層製造的浮水印技術，將浮水印或特殊標籤加入由三維列印機所產生的物體上。研究成果至少可以用來(一)保障產品與模型的智慧財產權、(二)防止產品偽造或變造、(三)進行產品與模型的確認與分類。我們的浮水印嵌入技術與傳統方法不同，浮水印是以程式碼方式植入3D列印機的機器碼程式中，而不是加在模型的幾何資訊內；浮水印無法被去除、模糊化、或破壞，除非攻擊者不需要製造目標產品。浮水印的驗證是以虛擬3D列印和實體成像技術來完成，可以利用視覺或統計關聯性進行判別；辨識的錯誤率小，容易使用。因此我們的浮水印鑲嵌技術能夠保護基層製造產業鏈中的模型設計者、產品製造者、與終端使用者的權利與安全，對基層製造和相關事業會有正面幫助。我們的浮水印鑲嵌程序可以簡單描述如下:首先我們讀入產品的幾何模型檔，然後執行體素化計算，將模型轉成由小方塊組成的體素模型；接著在體素模型上面計算出一個距離場，在這個距離場裡，每一個體素會記錄它與模型表面的最短距離；因此我們可依照距離的值，將體素模型分成若干層。在下一個步驟中，使用者輸入一個距離值，我們將屬於這個距離值的體素取出，形成一個等值曲面。同時，使用者將這個曲面上需要被鑲入浮水印的區域找出來；然後利用材質貼圖的計算將浮水印鑲嵌在這個區域內；浮水印的鑲嵌技術可以用下面方法完成(一)將區域內的體素轉成空間體素、或(二)將這些體素的列印顏色改變。最後，我們利用自行開發的體素模型基層製造輔助軟體，將這個3維體素模型轉成3G列印機的G-codes程式，完成整個浮水印鑲嵌計算。我們驗證浮水印的方法有兩種:(一)利用3D列印機產生物體，然後用目視方法檢驗浮水印；(二)利用模擬器產生虛擬體素模型，再利用體積成像法，顯示浮水印；或使用統計方法計算浮水印出現的可信度。與傳統浮水印鑲嵌方法比較，我們的技術擁有下列優勢:浮水印是以機器碼方式隱藏於3D列印機的程式中，難以破壞。浮水印是鑲嵌於G-code程式中，因此可以用來保護G-code程式的版權。本研究的浮水印鑲嵌技術可以產生鏤空、陰刻、與陽刻效果，增進3D列印技術。

Keyword(s)

浮水印
基層製造
體素模型
智慧製造
Watermarking
layered manufacturing
volume models
intelligent manufacturing
copyright protection.

DSpace CRIS

Watermarking for Layered Manufacturing

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