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CISSP For Dummies, 4th Edition by Peter Gregory, Lawrence Miller

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Cryptography Alternatives

Technology does provide valid and interesting alternatives to cryptography when a message needs to be protected during transmission. Some useful options are listed in the following sections.

Steganography: A picture is worth a thousand (hidden) words

Steganography is the art of hiding the very existence of a message. It is related to but different from cryptography. Like cryptography, one purpose of steganography is to protect the contents of a message. However, unlike cryptography, the contents of the message aren’t encrypted. Instead, the existence of the message is hidden in some other communications medium.

For example, a message may be hidden in a graphic or sound file, in slack space on storage media, in traffic noise over a network, or in a digital image. By using the example of a digital image, the least significant bit (the right-most bit) of each byte in the image file can be used to transmit a hidden message without noticeably altering the image. However, because the message itself isn’t encrypted, if it is discovered, its contents can be easily compromised.

Digital watermarking: The (ouch) low watermark

Digital watermarking is a technique similar (and related) to steganography that can be used to verify the authenticity of an image or data, or to protect the intellectual property rights of the creator. Watermarking is the visible cousin of steganography — no attempt is made to hide its existence. Watermarks have long been used on paper currency ...

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