Spread spectrum image steganography

A method of decoding steganographic messages embedded within digital images comprising the following steps:

• filtering the digital image with a restoration filter to produce a restored digital image;
• subtracting the restored digital image from the digital image to produce a difference signal;
• deinterleaving the difference signal according to a key;
• replicating a pseudorandom spreading sequence according to a key;
• demodulating the deinterleaved signal with the spreading sequence to construct an estimate of the message;
• decoding the message with an error correcting code comprising a binary expansion of a Reed-Solomon code to produce a decoded message.

A method of steganography for concealing messages within digital signals comprising the steps of:

• encoding an input message with an error correcting code to produce an encoded message;
• generating a spreading sequence with a pseudorandom noise generator according to a key;
• modulating the encoded message by the spreading sequence using a piecewise linear technique to produce an embedded signal;
• and
• combining the embedded signal with a cover signal to produce a stegosignal in which the input message is embedded.

A method of steganography for concealing messages within digital signals comprising the following steps:

• encrypting an input message with a key and encoding the input message with an error correcting code to produce an encoded message;
• generating a spreading sequence with a pseudorandom noise generator according to a key;
• modulating the encodeded message by the spreading sequence to produce an embedded signal and interleaving the embedded signal to enhance recovery of the embedded signal, where the interleaving step is performed according to a key;
• combining the embedded signal with a cover signal to produce a stegosignal in which the input message is embedded;
• and
• quantizing the stegosignal to preserve the original the original dynamic range of the cover signal.

A method of steganography for concealing messages within digital images comprising the following steps:

• encrypting an input message with a key;
• encoding the input message with an error correcting code comprising a binary expansion of a Reed-Solomon code to produce an encoded message;
• generating a spreading sequence with a pseudorandom noise generator according to a key;
• modulating the encoded message by the spreading sequence using a piecewise linear technique to produce an embedded signal;
• interleaving the spread spectrum modulated signal according to a key;
• combining the embedded signal with a cover image to produce spread spectrum modulated stegoimage in which the input message is embedded;
• and
• quantizing the interleaved spread spectrum modulated stegoimage to preserve the original dynamic range of the cover image.