Watermarking and transferring material

A computer readable storage medium that includes at least one data structure configured to store information, which when executed by a computer causes the computer to perform a method of watermarking and transferring watermarked material in a system including a transaction server, first and second clients, a first apparatus for applying a perceptible watermark to the material and a second apparatus for removing the watermark, the method comprising steps of:

• transferring from the transaction server to the first apparatus (i) data for creating a watermark, the creating data including (a) data defining an invertible algorithm and (b) data for creating at least one security key associated with the algorithm and (ii) data for creating a material identifier;
• using said first apparatus to apply a material identifier to the material and to apply a perceptible watermark to the material in accordance with the invertible algorithm, wherein the perceptible watermark is applied to the material as part of a compression of the material, and the invertible algorithm provides a perceivable impairment to the material;
• transferring from the first client to the transaction server said material identifier and data for inverting the algorithm including said at least one key;
• transferring the watermarked material to the second client;
• deriving said material identifier from the material;
• transferring the identifier from the second client to the transaction server;
• subject to predetermined conditions being satisfied, transferring from the transaction server to the second apparatus watermark removal data associated with said material identifier, the removal data including the at least one key and data defining an algorithm for removing the watermark in conjunction with the at least one key;
• and
• using the second apparatus to remove the perceivable watermark using said removal data, so as to remove the perceivable impairment from the material.

A system comprising:

• a transaction server configured to transfer data for creating a watermark and data for creating a material identifier to a first apparatus, wherein the data for creating the watermark includes data defining an invertible algorithm and data for creating at least one security key associated with the algorithm;
• the first apparatus configured to apply a material identifier to the material and to apply a perceptible watermark to the material in accordance with the invertible algorithm, wherein the perceptible watermark is applied as part of a compression of the material, and the invertible algorithm provides a perceivable impairment to the material;
• a first client configured to transfer said material identifier and data for inverting the algorithm including the at least one key to a transaction server;
• the first client further configured to transfer the watermarked material to a second client;
• the second client configured to derive said material identifier from the watermarked material and to transmit the material identifier to the transaction server;
• the transaction server configured to, subject to predetermined conditions being satisfied, transfer watermark removal data associated with the material identifier to the second client, the removal data includes the at least one key and data defining an algorithm for removing the watermark in conjunction with the at least one key;
• and
• a second apparatus configured to remove the watermark using the removal data.