The practice of hiding information in e-pictures, MP3 music
files, or any binary data format that can be changed without invalidating the
data format as well as retain the appearance of being unaltered. Steganography
is successful because it is based on the fact that digital images and MP3 music
files are comprised of thousands of pieces of binary code instructing a
computer to color a pixel or to produce a certain sound. Because of the large
number of digital information pieces involved, a few can easily be changed to
convey secret messages without having a significant impact on the overall
effect produced for the normal eye or ear. The secret information tends to be
stored in the least important parts of a digital image or MP3 tune.
Consider the potential that steganography could have for
terrorists trying to communicate with each other over the Internet. In a
holiday e-picture, for example, dozens of pixels in the background could be
altered to convey an airlines schedule, and to some casual observer or to an FBI agent, the picture would likely
appear to be innocent because the majority of the pixels would be left
unchanged. However, anybody who was told where to look could access the
information hidden in the amended pixels, which could then be put together and
read.
Steganography involves a simple procedure that can be
performed with software purchased from stores or downloaded from the Internet. The main reason for using
steganography rather than cryptography is that anything encrypted tends to draw
attention to the fact that some important information is deliberately being
hidden.
See Also:
Internet; Federal Bureau of Investigation (FBI).
Carter, S. Clinic: What is Steganography? [Online, 2004.] ITSecurity.com
Website. http://www.itsecurity.com/asktecs/oct2301.htm.
From Greek and translating as
covered writing or
hidden writing, and dating to 440 B.C., steganography is the art or science, or system, of hiding the existence of a message. In
The Histories of Herodotus, the Greek historian Herodotus mentions several examples. Into the wood backing of a wax tablet, Demeratus carved a message warning his countrymen of an impending attack. He then applied the wax, which hid the message from view until it was removed by the intended recipient. Another method involved shaving the head of a slave and tattooing a message on his scalp. After the hair grew back enough to cover the message, the slave could be sent through enemy lines, and his head could be shaved again to read the message. More recently, microfilm dots have been hidden under postage stamps, or disguised as punctuation marks in typewritten letters. Contemporary stenography takes more technologically sophisticated forms, such as a message hidden in a data file, for example, in an HTML file, a JPEG file, or an MP3 file. Such a hidden file also is typically encrypted for additional security. See also
encryption and
watermark.
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