关键词: 隐蔽信道, 网络计数器, 离散无记忆信道

Abstract: To avoid the limits of previous network storage covert channels which transmit covert information generally through packet head manipulation, a new idea was presented by using the plentiful, public Web counters for storage to construct a covert channel. Therefore, the encoder and the decoder do not need to establish a direct network connection, thus avoid the surveillances of many firewalls and intrusion detection system (IDS). A general noisy discrete memoryless channel (DMC) was modeled and the iteration algorithm of the DMC’s capacity was realized by C program language to compute the channel capacity. Several methods such as using multiple counters to increase rate were presented. One technique using pseudorandom sequence to scramble the sending information was used to enhance the covertness and the antinoise capability of the channel. The relationships between parameters and channel’s performance were analyzed through experiment. The result shows that the covert channel is feasible.