We propose a novel audio watermarking scheme which can recover the original audio carrier perfectly if the watermarked audio is modified. Besides, we can adjust the maximum tampered rate allowed and the quality of watermarked audio flexibly as required. In the scheme, an efficient generalized integer transform is improved to embed watermark data which are composed of least significant bits(LSBs) of averages in each patch, reference-bits and check-bits. LSBs are needed in the inverse transform. Then, by comparing the extracted check-bits and calculated ones, the modified area can be localized. Finally, reliable reference-bits and samples data help us reconstruct the original audio without errors. The efficiency of the proposed method is theoretically and experimentally verified.
With the rapid development of information network,the computing resources and storage capacity of ordinary users cannot meet their needs of data processing.The emergence of cloud computing solves this problem but brings data security problems.How to manage and retrieve ciphertext data effectively becomes a challenging problem.To these problems,a new image retrieval method in ciphertext domain by block image encrypting based on Paillier homomophic cryptosystem is proposed in this paper.This can be described as follows:According to the Paillier encryption technology,the image owner encrypts the original image in blocks,obtains the image in ciphertext domain,then passes it to the third party server.The server calculates the difference histogram of the image in ciphertext domain according to the public key and establishes the index database.The user passes the retrieved image to the server.The server computes the differential histogram of the retrieved image by public key.Then,compares the similarity of it with the histogram in index database and selects larger similarity images in ciphertext and send them to the user.The user obtains the target image with the private key.The experimental results show that the method is feasible and simple.
兼顾嵌入容量和算法安全性,提出了一种基于整数变换的加密图像可逆信息隐藏算法。内容所有者利用变换密钥,选取相应的两相邻像素为一组进行整数变换。变换后的像素组受该整数变换特性的约束,使得其中任意一个最低有效位(LSB Least Significant Bit)被替换后,仍能恢复出原始像素组。因此,信息隐藏者可根据相同的密钥找到加密图像中已进行变换的像素组,利用嵌入密钥替换对应像素的LSB完成隐秘信息可逆嵌入。只有同时拥有变换密钥和嵌入密钥,才能正确提取嵌入信息;只有同时拥有变换密钥及加密密钥,才能恢复出原图像,所以算法安全性较高。实验结果表明,该算法能够有效地在加密域中直接进行信息的嵌入及提取,并在解密后无损地恢复出原图像;而且该算法的嵌入率可高达0.47 bpp(bit per pixel)。
