Steganography And Covert Channels

With modern communication technology and the rapid development of computer technology, especially the rapid development of network technology, computer network has entered into many areas of human society, our society has into information age. Secure communications has become more and more important. Information hiding technology can provide capability that it can transmission secret message and ensure information is not being tapped in an open, unsafe network. Information hiding techniques including steganography, Covert channel, digital watermark technology. This paper focuses on the first two techniques.The word steganography comes from Greek and means "hidden writting". Information hiding (steganography) is the secret hiding secret information in a non-confidential file content into. The form for any kind of digital media file, such as images, sound, video or general document and so on. Cryptography only hides the content of information, and information hiding techniques hides not only the content of information but also the existence of hidden information. That third party Eavesdropper do not know whether there is a general document which embedding secret information. The cryptography which is core of traditional information security and information hiding techniques are not mutually contradictory, competing technologies, but complementary.The information Hiding has formally presented at the international in 1992, the first session of the International Conference on Information Hiding 1996, held in Cambridge, The meeting promoted the theory of information hiding and Technical Research. Current major research focus in the using and detecting of steganography and digital watermarking technology.1997, Rowland C. H made can build covert channels based on TCP/IP protocol. After that appeared a lot of covert channel communications technology base of network model. This view Steganography, digital watermarking technology and the covert channel technology should be considered a branch of information hiding. Although they have different purposes,Steganography is to hide secret information in the normal information;Digital watermarking is to embed the copyright information in digital works;Covert channel technique is to hide the communication process itself. Steganography and digital watermarking technology is the use of redundant information of digital files to hide the information, and covert channel is to use the redundant information of protocol to hidde communication behavior.There is several steganography technologies, including steganography based on digital image files, steganography based on digital audio file and steganography based on digital video files. Section 2.1 of this paper we analyzed the steganography based on digital image file, and provide a steganography algorithm, compared to the previous steganography algorithm base on image file, this algorithm is better cover, which is hardly recognizable by third parties.This paper describes the Covert Channel technology, and implementation of several models. This paper consider that the Covert channel technology is not a separate technology, but a branch of information hiding technology. Its main purpose is that hiding communication behavior based on the existing network communication protocols. Covert channel technology to fight against the object can be divided into categories:network protocol based on the implicit behavior of hidden communication channel, through the re-use of TCP/IP protocol in passing secret information to certain fields, to fight against the network monitor. It looks like a general communication without any secret information.In Chapter 5 we have listed the common covert channels based on TCP/IP and the possible means of detection, and gives an scheme based on ICMP protocol to establish a covert channel; Through the operating system's kernel technology to establish network connection, we can construct establish network communication by using the raw socket, the target host's operator can not dispatch this connection, the technology to confront the object is the target host's operator; In a one-way communication process, if you want establish a communication that hiding the communication sources of information, you can put forward in this paper is 4.9 "bounce package" section, in this section, the network monitor can not track who is the real source of communication.