Anti-Forensics Techniques: Steganography, the art of hidden writing, has been in use for centuries. It involves embedding a hidden message in some transport or carrier medium and mathematicians, military personnel, and scientists have been using it. They all engage in changing the common language and transferring it through secret and hidden communication.
The history of steganography dates back to the Egyptian civilization. Today, with the emergence of the Internet and multimedia, the use of steganography is mostly digital in nature.
According to www.webopedia.com, steganography refers to “The art and science of hiding information by embedding messages within other, seemingly harmless messages. It works by replacing bits of useless or unused data in regular computer files with bits of different, invisible information.”
In general, forensic investigators should look out steganography across evidences that do not support encryption. When it is not possible to encrypt a file, the next best option for safe transfer used by the intruders is steganography, The best way to protect sensitive information is to camouflage it, instead of encrypting it. It is basically a supplement or alternative for encryption. However, an encrypted file can still hide information by using steganography. This way, there would be a double measure of protection, as the encrypted file, once deciphered, would not allow the hidden message to be seen. One has to use special steganography software to decipher the hidden message. Many websites allow people to download steganography software; they can be freeware or trial software. Usually, steganography involves messages that are out in the open for many people to view. This can go unnoticed, as the very existence of the message is secret. Steganographic messages or images are essentially “hidden in plain sight,” unlike cryptographic messages.
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In cryptography, the users cannot read the message as it is in the jumbled form. Therefore, it is correct to state that the investigators know the existence of the message. This also protects the information that is present in the cipher. When the investigator intercepts an encrypted message, it is quite damaging as it informs the enemy about its two-way communication_ Steganography takes the exact opposite approach, as the uninformed user have no idea that there is communication going on.
How Steganography Works
Following are the steps representing the steganography work process:
- Step 1: Alice (sender) embeds the secret message into the cover message (original message).
- Step 2: Stego message (message containing secret message) is sent via secured channel to Bob (receiver).
- Step 3: Bob receives the stego message.
- Step 4: Bold decodes the stego message through a key.
- Step 5: Willie (third person) who observes the communication process between Alice and Bob thinks that the message sent is a normal message.
Types of Steganography, based on Cover Medium
Steganography is the art and science of writing hidden messages in such a way that no one other than the intended recipient knows of the existence of the message. The increasing use of electronic file formats and new technologies has made data hiding more and more possible. Basic steganography can be broken down into two areas: data hiding and document making, Document making deals with protection against removal. It is further classified into watermarking and fingerprinting.
The different types of steganography are as follows:
- Image Steganography: Images are the popular cover objects used for steganography. In image steganography, the user hides the information in image files of different formats such as .png, .jpg, .bmp, etc.
- Document steganography: In the document steganography, user adds white spaces and tabs at the end of the lines.
- Folder Steganography: Folder steganography refers to hiding one or more files in a folder. In this process, user moves the file physically but still keeps the associated files in its original folder for recovery.
- Video Steganography; Video steganography is a technique to hide files with any extension into a carrying video file. One can apply video steganography to different formats of files such as .avi, .mpg4, .wmv, etc.
- Audio Steganography: In audio steganography, user embeds the hidden messages in digital sound format.
- Whitespace Steganography: In the white space steganography, user hides the messages in ASCII text by adding white spaces to the end of the lines,
- Web Steganography: In the web steganography, a user hides web objects behind other objects and uploads them to a webserver.
- Spam/Email Steganography: One can use Spam emails for secret communication by embedding the secret messages in some way and hiding the embedded data in the spam emails. This technique refers to Spam Email steganography.
- DVDROM Steganography: In the DVDROM steganography, user embeds the content in audio and graphical mode.
- Natural Text Steganography: Natural text steganography is converting the sensitive information into a user-definable free speech such as a play.
- Hidden OS Steganography: Hidden OS Steganography is the process of hiding one operation system into other.
- C++ Source Code Steganography: In the C++ source code steganography, user hides a set of tools in the files.
Questions related to this topic
- What is steganography and how it works?
- How is steganography used today?
- What are the types of steganography?
- What is the difference between steganography and cryptography?
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