Steganography - DOC

Document Sample
Steganography - DOC Powered By Docstoc
Steganography is the art and science of communicating in a way which

hides the existence of the communication , which is the art of hiding information in ways that prevent the detection of hidden messages . Steganography , derived from Greek , literally means " covered writing " . It includes a vast array of secret communications methods that conceal the message's very existence . These

methods include invisible inks , microdots , character arrangement, digital signatures, covert channels , and spread spectrum communications.

Steganography and Cryptography are cousins in the spy craft family. A message in cipher text , for instance , might arouse suspicion on the part of the recipient while an " invisible " message created with Steganography methods will not. In contrast to Cryptography ,where the " enemy " is allowed to detect, intercept and modify messages without being able to violate certain security premises guaranteed by a Cryptosystem ,the goal of Steganography is to hide messages inside other " harmless " messages in a way that does not allow any " enemy " to even detect that there is a second secret message present.

Now Steganography is gaining new popularity with the current industry demands for digital watermarking and fingerprinting of audio and video.

Steganography in images has truly come of ,powerful computers. The most

age with the invention of fast in image Steganography is

popular technique

Least Significant Bit Insertion . More precisely , as Kuhn puts it :

The goal of Steganography is to hide messages inside other harmless messages in a way that does not allow any enemy to detect that there is a second secret message present.

The advantage of Steganography is that it can be used to secretly transmit messages without the fact of the transmission being discovered .Often, using encryption might identify the sender or receiver as somebody with something to hide . For example ,that picture of your cat could conceal the plans for your company's latest technical innovation. However ,Steganography has a number of disadvantages as well .Unlike encryption ,it generally requires a lot of overhead to hide a relatively few bits of information . However , there are ways around this . Also, once a Steganographic system is discovered , it is rendered useless. This problem,

too , can be overcome if the hidden data depends on some sort of key for its insertion and extraction.

The next chapter presents a detailed discription about the what the whole project is all about and how it is implemented.


Object oriented analysis is basically concerned with the decomposition of a problem into its component parts and establishing a logical model to describe the system functions. We follow this analysis as for the project.

3.1 Object Oriented Analysis ( OOA ) approach consists of the following steps :
1) Understanding the problem :

This is the first step in the analysis process . The problem statement should be refined and redefined in terms of computer system engineering that could suggest a computer based solution . The problem statement should be stated , as far as possible , in a single , grammatically correct sentence . The problem statement provides the basis for drawing the requirements specification of both the user and the software . Therefore the problem statement is “ This project attempts to make use of the standard steganographic tool and some modified version of standard encryption algorithm to perform the task of data hiding for the purpose of observing privacy “.

3.2 Requirements Specifications :
Once the problem is clearly defined , the next step is to understand what the proposed to do. Based on the user requirements , the specification for the software should be drawn . The developer should state clearly

What outputs are required ?

A set of screens displaying the output of data hiding and retrieval of hidden data . What inputs are necessary ?

Various interactive inputs that take the user through the different stages encountered during the execution of the application . What processes are involved to produce these outputs ?

Entering the text , choosing the picture , encoding , decoding display .

Processor RAM Hard Disk Cache Monitor Keyboard Mouse : : : : : : : Pentium. 64 MB. 2 GB. 512 KB. SVGA Color Monitor. 101 keys. 2 buttons.

OPERATING SYSTEM A multimedia PC running a windows 98 , 2000 or XP operating system .

3.2.3 TOOLS

3.3 Identification of objects :
Objects can often be identified in terms of the real world objects as well as the abstract objects . Their applications can be best analyzed by using the data flow diagrams.

Design is concerned with the mapping of objects in the problem space into objects in the solution space and creating an overall structure and computational models for the system . This stage normally uses the bottom - up approach to build the structure of the system and the top- down functional decomposition approach to design the class member functions that provides services . The steganographic process basically involves encoding , decoding and checking if encodable . These are the basic functions of the class codec and the pic codec class . The encryption process is handled by the crypt and objects .The remaining objects are the various dialogs for display and interaction with the user .

3.4 The main aim:
The user should be able to conceal a text message in an image file without any visible alterations to the image as such. I.e. there should not be any noticeable changes to the coloring or the position of the various objects in the image.

3.4.1 Sub: aims:
It is preferred that we use a windows based front end.

The user should be able to pick out the image file he wants to use in the hiding process.

The format of the image files which can be used for the hiding process should be 24-bit bitmap.

User should be able to enter the text message he wants to hide.

User should be able to view the image before and after the hiding process is complete. It is preferable that a new image be created and displayed with the old image which will allow the user to compare the original image with the new one which will help him to decide whether his choice of image file was appropriate or whether he needs a new one.

User should be able to transfer the image freely without any problems. I.e. he should be able to copy the new image file. Send or trade it with others without any special hardware requirements other than the normal communication systems available with a computer.

There should be a encryption process to encrypt the text for better security.

The user must be able to save the image in which the message is hidden in any desired folder.

The user should be able to select and view the picture from which to decode.

When the decode is demanded the encryption key should be demanded and when entered the decrypted text displayed.

He should be able to save the decrypted text message in a file.

The picture inside picture option should have all the above qualities like view both, compare and decide whether to proceed, and also have an option to save the new image where the user chooses.

To retrieve the picture the user must be able to view it, and then retrieve and save the picture