Protecting Intellectual Property Using Digital Watermarks 1 Ben A. Holt Protecting Intellectual Property Using Digital Watermarks Ben A. Holt CMPT495 Topics in Computer Science: Computer and Data Security Montclair State University December 19, 2005 http://home.comcast.net/~sonholt/datasecurity.html Abstract The World Wide Web has become a content rich environment that encompasses almost every digital multimedia format available. Users’ accessibility of digital multimedia has also grown side by side with these sophisticated content providers. Copyright protection has joined the race and new techniques are being used to ensure the protection of intellectual property available in digital formats. Watermarks are being used to embed information into content for copyright protection. This provides protection for the owners of the property and authentication convenience for those using the content [1]. 1 Introduction The need for protection of web based digital multimedia has grown with availability but not only because of it. The ease of availability has grown with the adoption of broad band communications. Large files have become easy to transfer with the use of sophisticated compression techniques. All of these aspects have increased the need for protection and made it a more difficult task for those involved. The owner of the intellectual property has his/her choice of protection methods, each with a distinct set of pros and cons. Using digital watermarks for protection is equivalent to analog watermarks. Additional Information is embedded into the object or signal. Watermarks are being used for copyright protection not copy protection. Copy protection attempts toProtecting Intellectual Property Using Digital Watermarks 2 Ben A. Holt limit the access to the copyrighted material or inhibit the copy process overall [2]. Copyright protection inserts information into the digital multimedia object without changing the quality. The information can be extracted to identify the owner of the digital object. Digital watermarks fall under two major categories, perceptible and imperceptible. Perceptible images range from visual patterns similar to paper watermarks, logos, and copyright symbols. There is a wide range adoption of perceptible watermarks because they are tangible. The owner can see the watermark proving to be a more trust worthy method. The use of imperceptible watermarks is growing although it is an entirely different arena. Imperceptible watermarks can secure copyright information with transparent or invisible or inaudible additions to the original digital object. The digital watermark may be implemented as a strong or weak mark. Strong watermarks are robust and resist degradation when the original object is modified. In the event of an ownership dispute the information in a strong watermark is retrieved for owner authentication [3]. Weak watermarks change with changes to the original objects to flag modifications. 2 Watermark Embedding The owner of the original digital object needs the facility to embed a digital watermark. There are many methods that can be used to accomplish the former. The following scheme is an example of watermark embedding borrowed form a web application [1]. A hash function is used with the 7 most significant bits for color values and a secret key to generate a binary value that is used to substitute the least significant bit for every pixel.Protecting Intellectual Property Using Digital Watermarks 3 Ben A. Holt The entire process is key dependant and robust. The change of any pixel can result in detection. For an RGB image the following algorithm represents the method where f is the hash function described above: Pixel(I,J) = fr(R(i,j))+fg(G(i,j))+fb(B(i,j)) The verification of the watermark can be performed by checking the color relationship of the original the key and the hash function. The inverse function is used to check the least significant bit of each pixel. The same function can be used for authentication, detecting modifications or damage considering each pixel. The previous function is an example o digital watermarking using the spatial domain. Changes were made to the least significant bit and information was added to the original digital object. Another method takes a single watermark and spreads the information over several pre-determined pixels. Blocks of pixels can also be modified as groups or processed with a specific transformation. This is similar to the processes employed by compression algorithm like JPEG. The detection of the watermark is very difficult unless the attacker knows the algorithm used to place the watermark in the given set of pixels. 3 Watermark Recovery The first task is to recognize the image. This is a discussion in itself so the following is a brief discussion. An image can be defined by specific features. The features can be partProtecting Intellectual Property Using Digital Watermarks 4 Ben A. Holt of the original image or they can be added by the watermarking technique. This type of information is imbedded in the image to facilitate the watermarks recovery. On technique is to use a registration pattern that can be made visible by distorting the image or performing transforms. Groups of points that exist in the original image can be categorized and grouped to create a recognition point. These are referred to a feature points. A block of information is selected as a feature point and is examined and recorded at varying resolution. Feature point content can change when the resolution of the image is changed. This is commonly referred to as the fingerprint of a digital object. Once the image is identified, the original can be recovered along with any watermarks that are embedded in the image. If the original image is distorted cropped or damaged, the identification marks can be used to recover the original non-cropped or undistorted image. Recovering the original image then allows us to extract any watermark information that may be imbedded in the image [4]. 4 Protection As explained, Digital watermarking is being used a form of protection for intellectual property. It is analogous to creating a new file format that carries copyright information. The Serial Coe Management System developed by Philips and Sony used this exact method. This is a digital music file format that includes copyright information. The information is