An AST-based Code Plagiarism Detection Algorithm

In modern software engineering, software plagiarism is widespread and uncurbed, developing plagiarism detection methods is imperative. Popular technologies of software plagiarism detection are mostly based on text, token and syntax tree. Among these plagiarism detection technologies, tree-based plagiarism detection technology can effectively detect the code which cannot be detected by the other two kinds of technologies. In this paper, we propose a more effective plagiarism detection algorithm based on abstract syntax tree (AST) by computing the hash values of the syntax tree nodes, and comparing them. In order to implement the algorithm more effectively, special measurement is taken to reduce the error rate when calculating the hash values of operations, especially the arithmetic operations like subtraction and division. Results of the test showed that the measurement is reliable and necessary. It performs well in the code comparison field, and is helpful in the area of protecting source code´s copyright.