Enterprise Resource Planning (ERP) is a tool for integrating business activities across functional departments on different modules with the aim of improving the performance of the organization's resource planning, management and operational control. This is the service which is most widely used on cloud in these days. In nearly every survey done about cloud computing the top reason given for not adopting it is a concern over security. So it is very important to develop new techniques for security over cloud. This paper proposes a framework for security of an ERP system on cloud.