The effort to define guidance for authentication of software for arms control and nuclear material transparency measurements draws on a variety of disciplines and has involved synthesizing established criteria and practices with newer methods. Challenges include the need to protect classified information that the software manipulates as well as deal with the rapid pace of innovation in the technology of nuclear material monitoring. The resulting guidance will shape the design of future systems and inform the process of authentication of instruments now being developed. This paper explores the technical issues underlying the guidance and presents its major tenets.