如何将用户凭据从服务器安全地传递到客户端？

My goal is to launch an installation with admin credentials(user with install rights), In order to do this I need to pass these user credentials from a webservice. So the question is What is the most secure way I could pass this data. Keeping in mind the user of the end client is not logged in as an administrator but I would assume has access to the data during transport(ie I cannot count on channel security alone.)My goal is to launch an installation with admin