1. A method for determining credentials of a process, running at a first data processing system, when accessing a service at a second data processing system, said method comprising: creating, at the second data processing system, a set of credentials for said process in response to a first request received from said first data processing system; returning a value to said first data processing system; receiving, at the second data processing system, a second request from said first data processing system comprising said value; and using the value to determine said set of credentials for said process during access to the service at the second data processing system.