Steganography and Steganalysis
Steganography is the art and science of writing hidden messages in such a way that no one apart from the intended recipient knows of the existence of the
message. Both the recipient and the sender must know how to decrypt the hidden message. This is done with a key/algorithm.
Steganography is often confused with cryptology because the two are similar in the way that they both are used to protect important information.
Cryptography is the study of hiding information, while Steganography deals with composing hidden messages so that only the sender and the receiver know
that the message even exists. In Steganography, only the sender and the receiver know the existence of the message, whereas in cryptography the existence
of the encrypted message is visible to the world. Due to this, Steganography removes the unwanted attention coming to the hidden message
Steganography methods reduce the chance of a message being detected. If the message is also encrypted then it provides another layer of protection.
Therefore, some Steganographic methods combine traditional Cryptography with Steganography.
Steganographic techniques have been used for ages. The aim of steganographic communication back then and now, in modern applications, is the same: to hide
secret data in an innocently looking cover and send it to the proper recipient who is aware of the information hiding procedure. In an ideal situation the
existence of hidden communication cannot be detected by third parties.
For Example: In ancient Greece, people wrote messages on the wood, and then covered it with wax upon which an innocent covering message was written.
Depending on the nature of cover file, steganography can be divided into five types:
· Text Steganography
· Image Steganography
· Audio Steganography
Video Steganography
· Protocol Steganography
Steganography Terms
· Cover File: A file which has hidden information inside of it.
· Stego File: A file within which information is hidden.
· Redundant Bits – Pieces of information inside a Cover File which can be overwritten or altered without damaging the file.
· Message: The data to be hidden or extracted.
Steganography can be split into two types, these are Fragile and Robust.
· Fragile steganography involves embedding information into a file which is destroyed if the file is modified. It is useful in situations where it is
important to prove that the file has not been tampered with, such as using a file as evidence in a court of law.
· Robust marking aims to embed information into a file which cannot easily be destroyed. There are two main types of robust marking.
o Fingerprinting involves hiding a unique identifier for the customer who originally acquired the file and therefore is allowed to use it.
o Watermarks identify the copyright owner of the file, not the customer. Whereas fingerprints are used to identify people who violate the license agreement
watermarks help with prosecuting those who have an illegal copy. Watermarks are typically hidden to prevent their detection and removal
Non ethical Steganography
· With Steganography hackers can embed all sorts of malware to an unsuspecting user. Typically an image file is attached to an email with an attractive
header the user clicks on it and the embedded file gets executed.
· Terrorists can send messages to communicate with each other.
Steganography using Windows Command Prompt
This method is rather basic and isn’t especially secure, but is still a valid way of hiding a file inside another file and making it invisible. It’s done
simply by using the Command Prompt and the DOS Copy command and joining the files together. Place the Image file and secret document in a folder.
Zip the secret message document i.e message.txt using WinRar, 7Zip, etc.
Open the command prompt to join this two file.
copy /b [cover_image] + [compress_file_to_hide] [image_result_name] in my case it is copy /b image.jpg + message.rar stegoimage.jpg and then press enter.
The /b tells the copy command that the file is a binary file and the + sign simply tells copy to append the 2nd file to the 1st.
After that you can get the stegoimage which is similar to the cover image. Data extraction from this file is very easy. For seeing the hidden message file
you have to change the file extension i.e from .jpg to .rar.
After getting the rar file you have to extract it to get the desired secret message.
Steganography using MP3 File Hider
MP3 File Hider hides any type of file inside MP3 without changing its size and sound quality. The hidden file is encrypted and can be revealed only with
password.
Select the container MP3 file. Select the file you want to hide, after analyzing, software will show the size of hidden file. This size cannot be more than
of container mp3 file. Enter the password and click hide button and you can get the desired stego mp3 file in the same folder.
Select the container stego MP3 file. Enter the password and click Reveal button and you can get the secret message. Please note wrong password will cause
damaged result file.
Attempting to detect the use of steganography is called steganalysis. The primary step of this process is to identify a suspected stego media. After that
steganalysis process determines whether that media contains hidden message or not and then try to recover the message from it.
Hiding a message will most likely leave detectable traces in the cover medium. The information hiding process changes the statistical properties of the
cover, which is a steganalyst attempts to detect. The process of attempting to detect statistical traces is called statistical steganalysis.
The properties of electronic media are being changed after hiding any object into that. This can result in the form of degradation in terms of quality or
unusual characteristics of the media: Steganalysis techniques based on unusual pattern in the media or Visual Detection of the same.
If we have a copy of original file it can be compared to the suspect file. Many tools can be used for viewing and comparing the contents of a hidden file.
We can use notepad and hexeditor to identify inconsistence and patterns.
Conclusion
The methods used in the science of steganography have advanced a lot over the past centuries, especially with the rise of the computer era. Steganography,
especially combined with cryptography, is a powerful tool which enables people to communicate without possible eavesdroppers even knowing there is a form
of communication in the first place As more and more techniques of hiding information are developed and improved, the methods of detecting the use of
steganography also advance.
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