In this work a distributed video surveillance system based on a Client-Server architecture is presented. The proposed system is accessible from portable devices such as tablets, smartphones, etc. In a typical real-world scenario, for example in homeland security, it is useful to have portable devices that can receive in real-time a frame or a sequence of frames coming from a selected camera to prevent or to detect attacks (i.e. terrorist attacks, etc.). In the proposed system, a portable device knows only the address of the server (repository), and the repository sends to the portable device the list of the clients (nodes) which are connected with one or more cameras. When the portable device obtains the list of the nodes, it connects directly to a specific node and requests the images of its connected cameras. The whole system provides secure communication channel between all its components. The security of both the node-repository and the repository-portable devices communications is guaranteed by using a secure connection. The security of the node-portable devices interconnection is provided by a digital invisible watermarking algorithm that affects each image before sending it from the node to the portable devices. Each portable device can extract the watermark and verify the identity of the node.