With the encryption technology widely used and developed on Web, the attacker has been difficult to obtain information from the message in encrypted channel, but they can use traffic analysis to obtain valuable information. 随着加密技术在Web上的广泛应用与发展,攻击者已经很难从加密信道的消息中获得信息,但仍能通过流量分析来获取有价值的信息。