Abstract: A method provides a collection of data structures and subroutines in a software toolkit, for developing an application for playing digital content data. The method comprises steps of receiving previously encrypted content data encrypted with an encrypted key from an external source; storing the previously encrypted content data in a library; selecting one or more encrypted content data from the library to play; and decrypting each content data selected to be played with its unique encryption key, wherein the decrypting is performed in a tamper-resistant subroutine for deterring unauthorized access to the instructions for decrypting the content data and for deterring unauthorized access to the encryption key.

Abstract: A method to debug application interface calls made to a tamper-resistant software module. The method comprises the steps of: loading a first application to be debugged using a debugging application, wherein the application makes one or more function calls to a tamper-resistant software module. A debugger application for symbolically debugging the first application is run and the debugger application with an initialization file that performs the steps of: loading a client application running a client socket service; loading a server application running a server socket service; loading the tamper-resistant software module with one or more function calls made thereto by the first application. The client application translates the one or more function calls made to the tamper-resistant software module during the running of the debugger application into socket calls and returns any status received from the socket calls to the first application.

Abstract: A system for tracking usage of digital content on user devices. Electronic stores coupled to a network sell licenses to play digital content data to users. Content players, which receive from the network the licensed content data, are used to play the licensed content data. Additionally, a logging site that is coupled to the network tracks the playing of the content data. In particular, the logging site receives play information from the network, and the play information includes the number of times that the content data has been played by the associated content player. Also provided is a method for tracking usage of digital content on user devices. According to the method, a license to play digital content data is sold to a user, and the licensed content data is transmitted to a content player for the user.

Abstract: A system for tracking usage of digital content on user devices. Content sites for distributing digital content over a computer readable medium to users. The content sites associate unique content identifier with the content associated. Electronic stores coupled to a network sell licenses to play digital content data to users. The licenses contain a unique transaction identifier for uniquely identifying the transaction, and the licenses contain a unique item identifier for uniquely identifying at least one item in the transaction. Content players, which receive from the network the licensed content data, are used to play the licensed content data. The content players produce a purchase identifier based upon the mathematical combination of the content identifier, the transaction identifier and the item identifier.