Steganography tools

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Steganography architecture example - OpenPuff

A steganography software tool allows a user to embed hidden data inside a carrier file, such as an image or video, and later extract that data.

It is not necessary to conceal the message in the original file at all. Thus, it is not necessary to modify the original file and thus, it is difficult to detect nothing. If a given section is subjected to successive bitwise manipulation to generate the cyphertext, then there is no evidence in the original file to show that it is being used. to encrypt a file. An example of this method is described in a self-published science fiction novel. In that example a file is encrypted using a 1949 photo from a digital archive of National Geographic magazine.[1]

Architecture[edit]

Obfuscation layer1 - cryptography

Carrier[edit]

The carrier is the signal, stream, or data file into which the hidden data is hidden by making subtle modifications. Examples include audio files, image files, documents, and executable files. In practice, the carrier should look and work the same as the original unmodified carrier, and should appear benign to anyone inspecting it.

Certain properties can raise suspicion that a file is carrying hidden data:

  • If the hidden data is large relative to the carrier content, as in an empty document that is a megabyte in size.
  • The use of obsolete formats or poorly-supported extensions which break commonly used tools.
Obfuscation layer3 - whitening

It is a crypographic requirement that the carrier (e.g. photo) is original, not a copy of something publicly available (e.g., downloaded). This is because the publicly available source data could be compared against the version with a hidden message embedded.

There is a weaker requirement that the embedded message not change the carrier's statistics (or other metrics) such that the presence of a message is detectable. For instance, if the least-significant-bits of the red camera-pixel channel of an image has a Gaussian distribution given a constant colored field, simple image steganography which produces a random distribution of these bits could allow discrimination of stego images from unchanged ones.

The encoded content should be compressed then encrypted. Encrypting it provides a uniform noise source which can be modulated into the carrier. It then becomes a fox-and-rabbit problem of hiders and finders (i.e. camouflage escalation) in a signal detection sense. The prey gets better at hiding, the predators at detection. The sheer volume of modern (ca 2014) and inane high-bandwidth media (e.g., youtube.com, bittorrent sources. ebay, facebook, spam, etc.) provides ample opportunity for covert communication.

Chain[edit]

Hidden data may be split among a set of files, producing a carrier chain, which has the property that all the carriers must be available, unmodified, and processed in the correct order in order to retrieve the hidden data. This additional security feature usually is achieved by:

  • using a different initialization vector for each carrier and storing it inside processed carriers -> CryptedIVn = Crypt( IVn, CryptedIVn-1 )
  • using a different cryptography algorithm for each carrier and choosing it with a chain-order-dependent equiprobabilistic algorithm
Obfuscation layer4 - encoding

Robustness and cryptography[edit]

Steganography tools aim to ensure robustness against modern forensic methods, such as statistical steganalysis. Such robustness may be achieved by a balanced mix of:

If the data is detected, cryptography also helps to minimize the resulting damage, since the data is not exposed, only the fact that a secret was transmitted. The sender may be forced to decrypt the data once it is discovered, but deniable encryption can be leveraged to make the decrypted data appear benign.

Strong steganography software relies on a multi-layered architecture with a deep, documented obfuscation process.

Chi-square image steganalysis

Carrier engine[edit]

The carrier engine is the core of any steganography tool. Different file formats are modified in different ways, in order to covertly insert hidden data inside them. Processing algorithms include:

  • Injection (suspicious because of the content-unrelated file size increment)
  • Generation (suspicious because of the traceability of the generated carriers)
  • Ancillary data and metadata substitution
  • LSB or adaptive substitution
  • Frequency space manipulation

Tools comparison[edit]

Tools comparison (alphabetical order)
Program Image files Audio files Video files Document files Other support Notes
Anubis  ?[clarification needed] - - - - Open source
Steghide  ?[clarification needed] - - - - Open source (GNU General Public License)
BMPSecrets BMP, JPG, TIFF, GIF - - -  ?[clarification needed] Allowes to replace up to 50-60% of picture with your information[clarification needed (snake oil)]
DarkCryptTC BMP, JPG, TIFF, PNG, PSD, TGA, MNG WAV - TXT, HTML, XML, ODT EXE, DLL, NTFS streams RSD mode (RNG-based random data distribution)
ImageSpyer G2 BMP, TIFF - - -  ?[clarification needed] RSD algorithm implemented, plugin for Total Commander (StegoTC G2)
MP3Stego - MP3 - - - Open source
OpenPuff BMP, JPEG, PNG, TGA MP3, WAV 3gp, MP4, MPEG-1, MPEG-2, VOB, SWF, FLV Pdf - Freeware, 256-bit multi-encryption, Carrier chains, Multi-layered obfuscation
OpenStego BMP, PNG - - - - Open source
Outguess-rebirth JPG - - - - Portable freeware Windows (based on Outguess for Linux)
PHP-Class StreamSteganography PNG - - - - -
Red JPEG JPEG - - - - XT for Total Commander, LZMA compression, PRNG-based masking and distribution
S-Tools BMP, GIF Wav - - Unused floppy disk space -
Steg BMP, PNG, JPEG, GIF - - - - Symmetric and asymmetric key cryptography, runs on Win/Linux/Mac
StegaMail BMP, PNG - - - - 56bit encryption, zLib compression
Steganographic Laboratory (VSL) BMP, PNG, JPG, TIFF - - - - Open source
Steganography Studio BMP, PNG, GIF - - - - Different hiding methods (LSB, LSB Matching, SLSB, ...), Open source
StegFS - - - - Steganographic file system for Linux -

See also[edit]

Articles[edit]

References[edit]

  1. ^ "Timelines", by Bob Blink, Amazon Kindle, Page 189

External links[edit]