INTRODUCTIONUsageHistoryAlgorithmsAnalysisCounter MeasuresConclusion> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1Steganography Rob Carey and Brent McClain, Member, IEEE Abstract — In this paper, we discuss the relationship between steganography and cryptography. We look at the history of steganography and its usage today. Steganographic image algorithms are explained and an analysis of the attacks against them is given. The attacks against steganography and historical ciphers show great similarity and a comparison is drawn between the two. Also, methods for providing counter-measures to digital steganography are discussed. Index Terms— steganography, steganalysis I. INTRODUCTION The word steganography is derived from the Greek words meaning “covered writing” and as such it centers on the concept of hiding a message in plain sight. Steganography focuses on the means of communication and the development of a covert channel [1]. Cryptography on the other hand focuses on the message being communicated itself and the development of a covert message. Steganography focuses entirely on keeping the adversary completely unaware of the communication, while Robert Carey is with SPARTA, INC. [email protected] Brent McClain is with SPARTA, INC. [email protected] cryptography is focused on keeping the contents of the communication secret. These differences of purpose were first recognized during the 18th century when the two were split into separate fields of study which we are currently familiar with. Cryptography shares many common characteristics with steganography, although the functions of the two have remained largely separate. Importantly the implementation of both has started to converge, and in-line the attacks on both have begun to look remarkably similar. During the first parts of this paper, the differences between steganography and cryptography will be underscored with the two divergent purposes of both. The latter portion of the paper will then concentrate on the similarities between the two in implementation and weaknesses. This paper should draw a good comparison between steganography and cryptography and show where both are in their development compared to one another. II. USAGE Steganography is used by many different organizations such as governments, terrorists and dissidents. These organizations have the same goal to covertly send messages to another party.> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 2 Governments use steganography to hide messages in mediums that can be intercepted. An embassy may send messages containing steganographic message over unsecure lines using steganography to ensure security. A spy may use steganography to avoid arousing suspicion when communicating with their handler. Different forms of steganography that can be used will be discussed later in the paper. This same technology allows terror groups like al-Quada, Hamas and Hezbollah to hide maps and communications in images on pornographic websites and other places on the internet [2]. It is very hard to detect this these messages due to the fact that there are over 4.2 million pornographic websites [3] out there. The World Wide Web is the perfect place for a “dead drop”. Terrorists can post an image with a target listed embedded in the image, thousands can see it but only the person who knows the algorithm and the key will get the target list. There are some positive uses for steganography, it can be used to get past censors and thwart eavesdroppers. Chinese dissidents can circumvent the censors in their county by encoding messages in images and posting those images on government approved sites. A hacking group named Hacktivismo has created a program called Camera/Shy [4] to allow Chinese dissidents to easily utilize steganography. Another positive use of steganography is watermarking. Watermarking is related to steganography because it puts data in a media to identify a media’s owner. This can be seen on any nightly news program in which the stations logo is usually displayed in the corner of the screen. Other watermarks may not be found in the open, like the stations logo. Watermarks are used in the distribution of pre-release movies. These watermarks are hidden and difficult to remove, and they allow the movie companies to trace back the original recipient of the movie. This is helping the FBI and the Motion Picture Association of America combat piracy [5] by finding the source of the information. Different forms of Digital Steganography Digital steganography can use many different digital mediums, TCP/IP packets, MP3 files [7], email [8], file systems [9] and images are just a few examples. TCP/IP packets can contain data in the unused reserved fields. Below in the TCP header there are 6 reserved bits [6] in which you could place data or the padding field is available. Figure 1. TCP Header format [6] Placing data in either one of those fields violates the RFC and is easy to detect. Craig Rowland has created a program called Convert_tcp [7] which utilizes the sequence number and the acknowledgement number to hide the data. One can use MP3s to hide information or provide a watermark. Data is hidden during the compression that> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 3creates the mp3 [8]. The major drawback with this method is the hidden information is lost if the mp3 is recompressed or decompressed. Computer users constantly receive unwanted junk email AKA spam. This provides the perfect medium in which to hide information. Some programs will adjust white space, while others use grammar and insert words to hide data. One program that does this is Spam Mimic [9], an example is shown in Figure 2. Dear Friend , Especially for you - this breath-taking news . If you are not interested in our publications and wish to be removed from our lists, simply do NOT respond and ignore this mail . This mail is being sent in compliance with Senate bill 1916 ; Title 7 ; Section 302 . THIS IS NOT MULTI-LEVEL MARKETING ! Why work for somebody else when you can become rich as few as 55 DAYS . Have you ever noticed most everyone has a cellphone and more people than ever are surfing the web . Well, now is your chance to capitalize on this ! WE will help YOU decrease perceived waiting time
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