"Uniform Office Format" (UOF) is the Chinese national standard for office document format. It aims to solve the problem that the office document format is not unified. It is helpful for information sharing and document exchange. Moreover, it improves the Chinese office software's compatibility, and establishes the foundation for the document information exchange. Through the study of Specifications for the Syntax and Processing of UOF and XML Encryption/ Signature, we proposed a set of APIs which ensure the confidentiality, integrity, and authentication of the UOF documents. The API is implemented by Java Cryptography Architecture, Java Cryptography Extension, Dom4j, and XPath technologies on Java platform and is confirmed to XML Digital Signature APIs (JSR105) and XML Digital Encryption APIs (JSR106) Specifications. Every interface and class is designed according to the rules that should keep high cohesion inside module and low coupling between modules. It also implements a special set of APIs for security UOF documents. Furthermore, a set of test cases together with a GUI program are developed to verify the availability and correctness of the system. It is believed that this project will contribute a lot to the research and adoption of the Specification for the Syntax and Processing of UOF Encryption/Signature.