HOW TO SECRETLY SEND A CONFIDENTIAL MESSAGE

BY USING STEGANOGRAPHY

Since ancient age, people have many ways to send the confidential message in other to hide message from unauthorized person meanwhile the message securely received by addressee. One of the oldest forms of long-distance communication is smoke signal that is visual communication way used by North American Indigenous peoples who started a fire to form a smoke that has specified meaning conveyed by the location where the smoke sent. Smoke signal also used by Polybius who invented a system of converting Greek alphabetic character into numeric character enabling message to be easily signaled by holding sets of torches in pairs. This idea, known as “Polybius square”, also suitable for cryptography and steganography. The first recorded uses of steganography can be traced back to 440 BC. Until now steganography is still useable and keep developing along with development of progressive technology. The modern steganography entered the world in 1985 with the advent of personal computers being applied to classical steganography problems.

 

Steganography is the art and science of hiding the fact ongoing communication by concealing a message, image, or file within another message, image, or file. Steganography comes from the acient Greek words “steganos” meaning ‘covered, concealed, or protected”, and “graphein” meaning writing. Generally, the hidden message will appear to be part of something else, images, articles, shopping list, or some other text. Unlike cryptography, steganography hide a confidential message in such a way so that it appears a plain message then the message does not attract attention to itself as an object of inspection. In other words, steganography able to conceal message in a medium without arouse suspicion. In this way, steganography is not only concerned with hiding the fact that the confidential message is being sent but also concealing the contents of the message. It is slight possible unauthorized person know that the secret message is being sent, let alone the contents.

Recently people are very common in using computer and internet for exchange information. The further progressive technology allow unauthorized people to access stored data, even to interrupt information exchange process, steal information through internet connection. This condition increases the requirement of secret way to send message. Consequently, steganography of concealing information within computer file keep advancing as technology progress. One of the triggers in steganography technique development is steganalist attack which is successful cracking message that hidden using widely known steganography method. So people continue to build the new steganography application program to keep their confidential message secretly send and securely received only by intended person.

Here we will talk about two steganography methods. The methods are steganography using pixel value differencing (PVD) spiral and steganography application using ID3V2 in the MP3 audio file. As we mentioned before steganography is made with the intention of hiding information in some medium in certain way so that the confidential message contained in medium is likely undetectable by human eyes. PVD is inserting message byte into the difference in bytes of the applied medium. This steganography use the modified PVD. To make the message extraction more difficult the modification will be carried out on the pixel pick up pattern using spiral pattern to form pixel pair. This PVD method apply the value difference in one pixel with that of other pixel, then the value deference value of pixel is used to insert confidential message in the other medium. Having the message been inserted into the message storage medium, the pixel value will be change in accordance with the PVD calculation formula. Due to its pixel pair has orderly pattern and the method has already known by many people, there is possibility the message insertion can be decrypted by unauthorized person. Therefore, PVD is modified by change the way of pick up the pixel pair pattern. The new way is picking up one pixel in the first row of image then one pixel in the last column then proceeded to pick up one latest row at the end, next one of the first pixel column. This way is repeated until all pixels have been picked up. Remember that once the pixel being picked up it will never picked up again to be combined with other pixel to form the next pixel pair. In this way, the unauthorized people will be more difficult to extract the confidential message inserted in the message storage medium.

As for steganography application program using the ID3V2 in the audio file on mobile phone the new way is make use the part of ID3V2 to conceal a confidential message, usually the steganography technique on audio make use the main body of the audio file. This steganography application conceal the confidential message on the ID3V2 Tag that is usually used on audio file for storing the additional data such as the information of singer’s name, song title, album title, even album cover figure. On this design, the MP3 file is chosen as file stego because the MP3 file format has been known and has very highly traffic in Internet so that it not arouse suspicion that there is a hidden message within the file. The message concealment in the audio file use the Before All Frames (BAF) method where the message partition is hidden before each the MP3 frame so that hiding message do not spoil the sound quality. As additional security this design applies McEliece cryptosystem which use relative huge matrix as public key. Nowadays the information really brings out mobile aspect, therefore this designed audio steganography programe make use of Android mobile platform. It proves that mobile platform can be applied to run steganography program. Having tested, the result is message can be inserted to the MP3 file and after decrypt the message can be read without any slightest change. Based on human hearing the sound is not changed at all. The sound quality doesn’t change because the sound is inserted outside the reach of the existing MP3 frame so that it does not change composition of the sound data at all. However no matter how unbreakable the method will be cracked someday so the requirement of new method will not terminate. We always need new method and it make the steganography technology keep improving.