Use of pseudocode to protect software from unauthorized use

摘要

Three methods are disclosed for protecting software applications from unauthorized distribution and use (piracy). The first method involves using values generated by a conventional ESD (Electronic Security Device) to encrypt and/or decrypt user data (such as a file) that is generated and used by the application. In a preferred embodiment, the user data is encrypted (such as during a write to memory) using values returned by the ESD, and the user data is later decrypted using like values returned by a software-implemented ESD simulator. The second and third methods involve the use of special development tools that make the task of analyzing the application's copy protection code (such as the code used to encrypt and/or decrypt user data) significantly more difficult. Specifically, the second method involves using pseudocode to implement some or all of the application's copy protection functions. The pseudocode for a given function is generated (preferably in encrypted form) from actual code using a special development tool, and is then imbedded within the application together with a corresponding pseudocode interpreter. The interpreter fetches, decrypts and executes the pseudocode when the function is called. Because no disassemblers or other development tools exist for analyzing the pseudocode, the task of analyzing the copy protection functions becomes significantly more complex. The third method involves the use of a special obfuscation tool to convert the code for selected copy-protection functions into unnecessarily long, inefficient sequences of machine code. In one implementation of the obfuscation tool, the developer can control the quantity of code that is generated by specifying one or more control parameters. The three methods can also be used to protect software license management systems from security attacks.