US 6,681,029 · Granted 2004-01-20

Decoding steganographic messages embedded in media signals

A decoder process reads a message steganographically encoded in a composite signal. One decoding process operates on a potentially modified version of the composite signal. The message is comprised of one or more symbols, each being associated with predetermined signal characteristics. The decoding process correlates these predetermined signal characteristics with the potentially modified composite signal to decode message symbols. Another decoding process analyzes a potentially modified version of the composite signal to gather evidence of signal characteristic associated with a message symbol. Based on the evidence, it determines whether the message symbol is present in the potentially modified version of the composite signal. Yet another decoding process analyzes the composite signal to gather evidence of characteristics associated with the message symbols in the message. Based on the evidence, it estimates message symbols. It compares the estimated message symbols with one or more message symbols known to be included in the message to assess whether the composite signal has a valid message.

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