Steganography is the practice of concealing a file, message, image, or video within another file, message, image, or video. The word steganography combines the Greek words steganos (στεγαν?ς), meaning "covered, concealed, or protected", and graphein (γρ?φειν) meaning "writing".

The first recorded use of the term was in 1499 by Johannes Trithemius in his Steganographia, a treatise on cryptography and steganography, disguised as a book on magic. Generally, the hidden messages appear to be (or be part of) something else: images, articles, shopping lists, or some other cover text. For example, the hidden message may be in invisible ink between the visible lines of a private letter. Some implementations of steganography that lack a shared secret are forms of security through obscurity, whereas key-dependent steganographic schemes adhere to Kerckhoffs's principle.[1]

The advantage of steganography over cryptography alone is that the intended secret message does not attract attention to itself as an object of scrutiny. Plainly visible encrypted messages—no matter how unbreakable—arouse interest, and may in themselves be incriminating in countries where encryption is illegal.[2] Thus, whereas cryptography is the practice of protecting the contents of a message alone, steganography is concerned with concealing the fact that a secret message is being sent, as well as concealing the contents of the message.

Steganography includes the concealment of information within computer files. In digital steganography, electronic communications may include steganographic coding inside of a transport layer, such as a document file, image file, program or protocol. Media files are ideal for steganographic transmission because of their large size. For example, a sender might start with an innocuous image file and adjust the color of every 100th pixel to correspond to a letter in the alphabet, a change so subtle that someone not specifically looking for it is unlikely to notice it.

orig source:


used in the movie: Along Came a Spider


... see on how you can be the spider...

       The basic usage is as follows:

         $ steghide embed -cf picture.jpg -ef secret.txt
         Enter passphrase:
         Re-Enter passphrase:
         embedding "secret.txt" in "picture.jpg"... done

       This command will embed the file secret.txt in the cover file picture.jpg.

       After  you  have  embedded  your  secret  data as shown above you can send the file picture.jpg to the person who should receive the secret message. The receiver has to use steghide in the following way:

         $ steghide extract -sf picture.jpg
         Enter passphrase:
         wrote extracted data to "secret.txt".

       If the supplied passphrase is correct, the contents of the original file secret.txt will be  extracted  from  the  stego  file  pic?
       ture.jpg and saved in the current directory.

       If  you have received a file that contains embedded data and you want to get some information about it before extracting it, use the
       info command:

         $ steghide info received_file.wav
           format: wave audio, PCM encoding
           capacity: 3.5 KB
         Try to get information about embedded data ? (y/n) y
         Enter passphrase:
           embedded file "secret.txt":
             size: 1.6 KB
             encrypted: rijndael-128, cbc
             compressed: yes

       After printing some general information about the stego file (format, capacity) you will be asked if  steghide  should  try  to  get
       information  about  the embedded data. If you answer with yes you have to supply a passphrase. Steghide will then try to extract the
       embedded data with that passphrase and - if it succeeds - print some information about it.

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