高安全等级网络中信息隐蔽分析和实用抵抗模型
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摘要
随着信息化进程的发展,国家根据重要程度把信息系统分成不同等级,高等级的信息系统需要更高的安全防护能力。当不同的信息域之间需要交换数据时,若网络中存在恶意的程序或用户,就可能利用某些隐蔽通信技术泄露敏感数据。
合法通讯使得承载其上的隐蔽通讯必然存在,因此在安全程度较高的网络需要对隐蔽通道进行分析,并采取手段进行定位、消除、限制和检测。
本文从隐通道抵抗角度出发,以构造一个实用的高等级安全网络中的隐蔽信息抵抗模型为目标,进行了理论分析并阐述了实际应用中需注意的问题。
首先,本文综合了以往的相关网络隐蔽通道研究,针对信源信息熵的不同,提出了基于信息熵的三种分类,把隐蔽通道分为变熵、定熵和零熵,其中零熵是一个新的分类,并根据隐蔽方如何利用显式信源提出了下一级子分类。
其次,本文详细描述了定熵隐蔽通道的检测,提出了两种检测方法,属性偏移检测和卡方检测,两种方法从不同的方面提高了检测的效果。对新提出的零熵分类,由于没有相关的检测方法做比较,给出了看守参数设置和隐蔽通道容量的关系,使看守可以根据对隐蔽通道的容忍程度配置不同的参数。
然后,本文把看守和可信终端节点相结合,通过在可信终端上建立可信根,并经过可信链传递到网络上,使看守和终端节点互相认证,看守上预先配置文件的证明信息对数据进行校验,能够较好的解决由于受限于权限和计算能力的看守带来的隐蔽通道。
最后,文章根据前文的分析,提出了实用的网络看守模型,模型采用三机体系结构来提高自身的安全,信息落地来消除底层隐蔽通道,配置通道来对数据传输分别控制,讨论了几个具体实现碰到的问题。给出并分析了一个实际应用中的典型案例,指出其能够回避的网络隐蔽通道和尚存的隐蔽通道容量。根据例子说明,本文提出的看守模型能够较好的解决高等级安全网络的隐蔽信息泄露问题。
With the development of information network, Information systems are classified into different grades in our country, highly security level network needs higher defence. When data exchange is reqired between domains, if there exist some malisious users or processes, some covert communication methods can be used to leak information.
Covert communications are inevitable over legal communication if the legal exists. So in highly security level network, covert channel must be analysed, and some counter measurements must be taken.
This thsis does some research based on covert channel counter measurements.In order to make up a practical warden model for data exchange between different domains, and analysed covert channels, and presented practical problem met in reality.
First, we describe related covert channel research works. Then we propose three kinds of covert channels based on different entropy aspect, we classify them into varity entropy, constant entropy and zero entropy covert channel. Among them, zero entropy is a new species, and we further devide them by how to utilize the overt source.
Second, we propose two methods of detection for constant entropy covert channel. The attribe shift method and the pearson chi-square method, the two methods improved the effect with different aspect. For the new proposed zero entropy channel, we gave the relation between warden parameter selection and channel capacity.
Then, limited by calculation and authorization, some covert channels should not be countered on network solely. So we integrate the warden and trusted endpoint. Through setting up root of trust on endpoints, and expanding it to network, the warden can verify files based on the configuration information in advance.
Finally, we propose a practical warden model which adopting 3-hosts and information landing, discuss some practical problem in reality, and give an example.
合法通讯使得承载其上的隐蔽通讯必然存在,因此在安全程度较高的网络需要对隐蔽通道进行分析,并采取手段进行定位、消除、限制和检测。
本文从隐通道抵抗角度出发,以构造一个实用的高等级安全网络中的隐蔽信息抵抗模型为目标,进行了理论分析并阐述了实际应用中需注意的问题。
首先,本文综合了以往的相关网络隐蔽通道研究,针对信源信息熵的不同,提出了基于信息熵的三种分类,把隐蔽通道分为变熵、定熵和零熵,其中零熵是一个新的分类,并根据隐蔽方如何利用显式信源提出了下一级子分类。
其次,本文详细描述了定熵隐蔽通道的检测,提出了两种检测方法,属性偏移检测和卡方检测,两种方法从不同的方面提高了检测的效果。对新提出的零熵分类,由于没有相关的检测方法做比较,给出了看守参数设置和隐蔽通道容量的关系,使看守可以根据对隐蔽通道的容忍程度配置不同的参数。
然后,本文把看守和可信终端节点相结合,通过在可信终端上建立可信根,并经过可信链传递到网络上,使看守和终端节点互相认证,看守上预先配置文件的证明信息对数据进行校验,能够较好的解决由于受限于权限和计算能力的看守带来的隐蔽通道。
最后,文章根据前文的分析,提出了实用的网络看守模型,模型采用三机体系结构来提高自身的安全,信息落地来消除底层隐蔽通道,配置通道来对数据传输分别控制,讨论了几个具体实现碰到的问题。给出并分析了一个实际应用中的典型案例,指出其能够回避的网络隐蔽通道和尚存的隐蔽通道容量。根据例子说明,本文提出的看守模型能够较好的解决高等级安全网络的隐蔽信息泄露问题。
With the development of information network, Information systems are classified into different grades in our country, highly security level network needs higher defence. When data exchange is reqired between domains, if there exist some malisious users or processes, some covert communication methods can be used to leak information.
Covert communications are inevitable over legal communication if the legal exists. So in highly security level network, covert channel must be analysed, and some counter measurements must be taken.
This thsis does some research based on covert channel counter measurements.In order to make up a practical warden model for data exchange between different domains, and analysed covert channels, and presented practical problem met in reality.
First, we describe related covert channel research works. Then we propose three kinds of covert channels based on different entropy aspect, we classify them into varity entropy, constant entropy and zero entropy covert channel. Among them, zero entropy is a new species, and we further devide them by how to utilize the overt source.
Second, we propose two methods of detection for constant entropy covert channel. The attribe shift method and the pearson chi-square method, the two methods improved the effect with different aspect. For the new proposed zero entropy channel, we gave the relation between warden parameter selection and channel capacity.
Then, limited by calculation and authorization, some covert channels should not be countered on network solely. So we integrate the warden and trusted endpoint. Through setting up root of trust on endpoints, and expanding it to network, the warden can verify files based on the configuration information in advance.
Finally, we propose a practical warden model which adopting 3-hosts and information landing, discuss some practical problem in reality, and give an example.
引文
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