中文摘要：

提出一种密文图像中的可逆数据隐藏系统，可在加密的医学图像中嵌入附加信息，还可无损恢复原始图像．系统包括发送端、服务器端和接收端三部分，发送端使用流密码对原始医学图像进行加密并发送到服务器端；服务器端使用基于循环移位的方法在密文中隐藏附加信息，同时不改变密文图像的数据量；接收端下载含附加信息的密文图像，不仅可提取附加信息，还可无损恢复原始医学图像．与传统方法相比，该方法提高了密文中的数据嵌入容量．

英文摘要：

This paper proposes a scheme of reversible data hiding for encrypted medical images. The proposed scheme contains three parts： a sender, a server and a receiver. The content owner encrypts the original medical image using a stream cipher and uploads the encrypted image to the server. The data-hider on the server hides additional data into the encrypted medical image using a circulating shift method that preserves the size of the encrypted image. The receiver downloads the encrypted image containing additional data, extracts the additional data precisely, and recovers the original medical image losslessly. Compared with some previous schemes, the ity. proposed method has larger embedding capac-