Steganography / hiding in plain sight

Steganography is the art and science of hiding that communication is happening. Classical steganography systems depend on keeping the encoding system secret, but modern steganography is detectable only if secret information is known, e.g. a secret key. Because of their invasive nature, steganography systems leave detectable traces within a medium's characteristics. This allows an eavesdropper to detect media that has been modified, revealing that secret communication is taking place. Although the secrecy of the information is not degraded, its hidden nature is revealed, defeating the main purpose of Steganography.

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