The Design And Implementation Of Covert Communication System Parasitic On Anonymous Network

Traditional covert communication systems built using traditional covert channel techniques often consist of static single paths,which can easily expose the identities of the communicating parties.The core idea of some new technologies is to avoid the establishment of a direct connection between the parties.These new technologies can be divided into two categories:introducing a third-party server and constructing a covert channel using decentralized networks.However,they also bring new issues.For example,introducing a third-party server may result in the functionality of the covert channel being influenced by its commercial strategy.Using a decentralized network may lead to insufficient forward security and performance issues.Therefore,it is of great significance to design and implement a covert communication system that possesses high security,strong concealment,and good performance.In this paper,we focus on the Tor network as the research object.The Tor network is a widely used anonymous network that provides hidden services,allowing the communicating parties to conceal their respective IP addresses.We conduct research and analysis on various entities within Tor’s hidden services and utilize hidden service descriptors as the carrier of covert information to construct a covert channel.The main contributions of this paper are as follows:(1)We design a covert channel architecture that parasitically utilizes the Tor anonymous network.In this architecture,the hidden service directory servers serve as relay servers to facilitate communication between the parties.This architecture achieves isolation between the communicating parties,avoiding direct connections and instead utilizing the relay servers as intermediaries.(2)To adapt to the architecture of the covert channel,we design an acknowledgement and retransmission mechanism based on protocols such as TCP to achieve the "burn after reading" functionality.We utilize Tor’s hidden services,erasure coding,and other techniques to implement fragmentation and redundancy.We also modify the asynchronous I/O mechanism of the Tor process to meet the high-concurrency requirements of our system.(3)We develop a cross-platform desktop application using the Electron platform and the sqlite3 database.This application enables users to communicate using the developed covert channel.We provide applications for both Linux and Windows platforms.Additionally,we test and validate the performance and features of this covert communication system.