Reversible watermarking using expansion, rate control and iterative embedding

A method for reversible watermarking of a host data set, the method comprising:

• using a computer programmed to perform the acts of:
• applying a series of two or more reversible, integer to integer transforms of values in the data set to produce a set of modifiable values for carrying a reversible watermark;
• modifying the modifiable values to embed the reversible watermark in the host data to produce watermarked transformed values;
• and
• computing an inverse of the two or more reversible transforms in the series on the watermarked transformed values to produce a watermarked host data set.

A digital watermark encoder for watermarking a data set, the encoder comprising:

• memory for storing the data set;
• and
• digital circuit in communication with the memory for reading the data set and for applying a vector difference transform to vectors in the data set, wherein the vector difference transform transforms selected sets of values in a corresponding vector into difference values;
• wherein the digital circuit modifies the difference values to embed auxiliary data into the data set, and applies an inverse vector difference transform to the modified difference values to produce a watermarked data set.

A digital watermark encoder for reversible watermarking of a host data set, the encoder comprising:

• a memory for storing the host data set;
• and
• a digital circuit in communication with the memory for reading the data set and for applying a series of two or more reversible, integer to integer transforms of values in the data set to produce a set of modifiable values for carrying a reversible watermark;
• wherein the digital circuit modifies the modifiable values to embed the reversible watermark in the host data to produce watermarked transformed values, and computes an inverse of the two or more reversible transforms in the series on the watermarked transformed values to produce a watermarked host data set.

A method of reading a digital watermark from a data set comprising:

• using a computer programmed as a digital watermark reader to perform the acts of:
• applying a vector difference transform to vectors in the data set, wherein the vector difference transform transforms selected sets of values in a corresponding vector into difference values;
• extracting auxiliary data from the difference values to obtain auxiliary data embedded into the data set, and restoring difference values to original values prior to embedding of the auxiliary data to produce restored difference values;
• and
• applying an inverse vector difference transform to the restored difference values to produce a restored original data set.

A method for reading a reversible watermark from a host data set, the method comprising:

• using a computer programmed to perform the acts of:
• applying a series of two or more reversible, integer to integer transforms of values in the data set to produce a set of modifiable values carrying a reversible watermark;
• extracting the reversible watermark from the modifiable values and restoring the modifiable values to restored values;
• and
• computing an inverse of the two or more reversible transforms in the series on the restored values to produce a restored host data set.