Abstract: An individual security program is randomly chosen by way of a respective key and is then packaged with a games program to provide an executable program file which is applied to a storage media, such as an optical disc. Whenever the security program is running, the object code it produces is obfuscated to make it difficult to overcome the protection by identifying and removing the security program. The obfuscated object code is produced by substituting a variable in source code with a function of the variable. When the source code is compiled to produce the object code, the function causes the variable to be presented in the compiled object code as a series of operations.

Abstract: The present invention relates to a method of copy protecting optical discs, such as CDs or DVDs. Instead of encoding data onto the CD-ROMs in a conventional manner which ensures balanced dc content, for copy protection the digital data is encoded and recorded onto the optical disc such that it is arranged to give some of the recorded digital data highly unbalanced dc content. Thus, for example, the DSV (digital sum value) value of the encoded data is recorded so that the DSV value changes continuously once 50 frames of data or more.