关键词: 电子印章, 数字水印算法, 篡改检测, 准确定位, 特征提取

Abstract: Aiming at the problems that the electronic seal digital watermarking algorithm has low feature extraction efficiency and low tampering positioning accuracy，a digital watermarking algorithm based on FAST（Feature from Accelerated Segment Test）corner feature was proposed. Firstly，OpenCV was used to extract the FAST corner features of the electronic seal image and separate their pixel values. Secondly，the feature point pixel value iwas encrypted by MD5 encryption algorithm and its message sequence was obtained. Then，according to the parity position interchange and equalization Rrordering the message sequence was rearranged. And then，the binary value corresponding to each electronic seal image pixel was determined according to a prespecified pixel binary look-up table. Finally，the watermark identifier was generated according to the encrypted message sequence and the binary look-up table result，which was embedded into the original electronic seal image to complete the watermark embedding. The experimental results show that compared with the digital watermarking algorithm based on Harris corner feature， the proposed algorithm reduces the feature extraction time by 86%，improves the tampering positioning accuracy by 60%，verifying that the feature extraction efficiency and detection accuracy are greatly improved. Therefore，the digital watermarking algorithm based on the FAST corner feature has higher practical engineering application value.

Key words: electronic seal, digital watermark algorithm, tamper detection, accurately locate, featurer extraction