Steganography tools

A steganography software tool implements a subset of the most general digital steganography process, allowing users to insert and extract hidden data into and from carrier files.

Contents 1 Architecture 1.1 Hidden data 1.2 Carrier 1.3 Chain 1.4 Cryptography 1.5 Carrier engine 2 See also 3 External links 3.1 Steganography tools directories 3.2 Articles 3.3 Workshops

Architecture

Novel users approaching steganography need to get acquainted with some common steganography-related terms and concepts

Hidden data

Data to be covertly communicated are usually referred to as hidden data. Steganography focuses on the covertly adjective. You're going to employ a steganography tool because the very existence of the data has to be secret and invisible. The tool can also perform some cryptography on the hidden data, but remember it is optional: data has to be invisible first.

Please notice also that, according to common public opinion:

• Cryptography plays a relevant role in public / trusted / legal data sharing
• Steganography plays a minor role in secret / obscure / illegal data sharing

Carrier

The carrier is the signal, stream, or data file into which the payload is hidden.

Take also a look to this practical definition of carrier:

• The audio/image/video/text/executable/repository file that, once processed,
  • will look and work as the original one
  • will hold inside part of or the whole hidden data
  • will raise no suspect sending it by email, sharing it through internet, carrying it out of the office, a.s.o.

From a user point of view:

• Carriers have to raise no suspect because of their size
  • small carriers with no data are very suspicious: What would you think about an empty word document with a 1Mb size?
  • huge carriers exchanged through internet are very suspicious: What about a downloadable set of DVD .vob files?
• Carriers have to raise no suspect because of their format
  • out of date file formats are very suspicious: What about a .wav downloadable telephone ringtone?
  • non standard file format extensions are very suspicious: What about a PDF reported as broken or corrupted by adobe reader?

Chain

When hidden data is split among a set of files you get a carrier chain.

Carrier chains are a main feature of every professional steganography tool, ensuring that you can't get the hidden data back:

• if one or more carriers are missing
• if one or more carriers have been manipulated (volatile steganography)
• if one or more carriers are not processed in the correct order

This additional security feature is usually 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

Cryptography

Users have to remember that steganography's main goal is invisibility. A good steganography tool should first ensure robustness against modern forensic methods, like statistical steganalysis. Strong cryptography, along with any other obfuscation process, is always welcome but should only be considered as a last-man-standing defense. Encoding (steganography) will deceive attackers and obfuscation (cryptography) will slow them down once you've been caught. People hiding sensitive data should consider deniable cryptography as an exit strategy.

Robustness against statistical steganalysis can be achieved by a balanced mix of:

• stream based cryptography process
• data whitening process
• encoding process

Steganography users should rely only on multi-layered architectures with a deep documented obfuscation process.

Carrier engine

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. Among these processing algorithms you can find:

• 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

See also

Steganography BPCS-Steganography

Steganographic file system Steganography detection

External links

Steganography tools directories

• Steganography software
• Network steganography software
• Steganography software

Articles

• Analyzing steganography softwares
• Steganalysis
• Niels Provos - Defending against statistical steganalysis
• Jessica Fridrich - Constructing good covering codes for applications in steganography

Workshops

• Workshop "Vision of the Unseen"
• Workshop "Information Hiding"
• Workshop "International Workshop on Network Steganography"
• Webinar: Steganography: Digital Data Embedding Techniques Overview (Scientist.By)