In this paper, a semi-fragile watermarking for image authentication, localization, and recovery scheme by using Tchebichef moments is proposed. We use robust invariant Tchebichef moments to generate the authentication feature, and use scaled Tchebichef moments to construct recovery information from low-frequency domain.. In order to improve the quality of watermarked image and keep the robustness of watermark, we applied HVS to adjust the embedding and extraction quantization step size. The proposed method provides a complete authentication process from RST attack estimation to image recovery. The proposed method has high accuracy of authentication, can localize and recover the tampered region successfully and is robust to JPEG compression and AWGN operations.

在網路高速發展的環境下，多媒體內容之認證越來越重要。半脆弱型浮水印技術可以同時保有脆弱型以及強韌型浮水印的特性，達到可同時對接受端做影像內容之認證及偵測被惡意攻擊之區塊。
在本篇論文中，我們提出了一個完整的半脆弱型浮水印之影像認證系統，可以從預測幾何攻擊參數、影像認證、指出遭竄改區塊到回復影像。我們提出的系統主要架構在Tchebichef moments上，因為Tchebichef moments是屬於離散域的moments function，具有很好的影像回復特性，而invariant Tchebichef moments則是具有很好的強韌性。因此我們使用這兩個特性來做為影像回復資訊以及影像特徵認證。
從實驗結果得知，我們提出的方法可以有高準確度的認證，並且成功地指出及回復被竄改的區塊，也因為我們的方法有根據人眼視覺系統做調整，所以我們可以得到較好的影像品質。

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