The present invention generally relates to computer security, and more specifically, related to registration and authorization cross multiple domains. In an aspect, a computer-implemented method, computer-implemented system, and computer program product for cross domain registration by a source domain is provided. A request is sent by a source domain to register the source domain as a trusted domain of a target domain. An approval of the request is received by the source domain. The source domain issues a key to an application of the source domain for accessing the target domain.