Abstract: The safety of network data is becoming more and more serious. Digital signature of data file can be implemented by using Java security API, and the data file can be safely transferred on network. This paper introduces basic procedure of digital signature. It illustrates about the algorithm of digital signature, describes how to write Java programs to digital signature file in sender, and how to write Java programs to verify the signed file in receiver. At last it discusses the potentially unsafe factors of this method.

Key words: Java, network safety, digital signature algorithm