A mobile computing device has at least one processor and at least one memory together providing a first execution environment and a second execution environment logically isolated from the first execution environment. The following approach is taken to manage data items for an application executing the first execution environment. A trust relationship is established between a trust client in the second execution environment and a remote trusted party and the trust client receives one or more data items from the remote trusted party. On executing the application in the first execution environment, the trust client provides the data items or further data items derived therefrom to the application. Provision of these data items may be conditional upon a user authentication process. A suitable mobile computing device is also described.