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What's New-- The new edition contains most of the
original material with new chapters devoted to these topics:
- Keys--How to use a password or a shared secret to lock
the hidden image so that it can only be read by those with the right key.
- Ordering and Reordering--How to hide a message by reordering
a list. (Try out this demonstration applet.) How to defend against attackers
who reorder your information in transit.
- Spread Spectrum Techniques-- How to spread out a message
over a number of different pixels, words or other elements. This section shows
how to hide information that resists noise and attackers by relying heavily
on the solutions created by spread spectrum radio engineers.
- Synthetic Worlds--How to hide information by changing
the positions of letters on a page, monsters in a maze, clouds in a sky or
any parameter of data displayed on the screen. This technique is very useful
for protecting digital content and giving a message an innocuous cover.
- Steganalysis--Some steganographic algorithms for hiding
information in images are far from perfect. They leave behind tell-tale statistical
artifacts that reveal the existence of a message. This chapter explores some
of the techniques for identifying images with hidden information.
- Watermarks-- Protecting movies, photos, and music with
hidden information is one of the most attractive uses for steganography today.
This chapter shows how some of the techniques from the previous chapters can
be applied to this task.
- Mimic Code-- The original code for creating mimic functions
is now rewritten in Java. Download it here.
What's Old-- The first edition, published
in 1996, explored the topic of steganography long before the word reached
the general consciousness.
- Cryptography--An introduction to the basic details used
to scramble information. These tools are often combined with the steganography
to provide additional security.
- Error-Correcting Codes-- These codes can be used to make
hidden information more resilient and let you hide practically invisible
information.
- Secret Sharing-- How to split a message into several
pieces in a way that the message can only be recovered by those who hold
all of the pieces.
- Compression-- Algorithms that squeeze data into smaller
files are both the enemy of steganography and the basis for many algorithms.
On one hand, compression algorithms destroy the extra noise and randomness
in a file making it harder to slip in new information. On the other hand,
compression algorithms model data and they can be run in reverse to mimic
the data.
- Mimic Functions-- These hide data by mimicking the statistical
profile of some data. This is useful for acting like text or simply arranging
for some data to appear like another. Some of the more sophisticated versions
can model any kind of data that can be modeled with a logical framework.
- Using the Noise-- How to hide information in the noise
of image and sound files.
- DC Nets-- How to broadcast information so no one knows
who is speaking.
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