Figure 3. The application inside an isolated SPE cannot be observed or modified
hacker who has gained root or hypervisor privileges is not a threat to an application executing on an isolated SPE. The supervisory privileges will not enable him to control the application, nor will it allow him to read or write the memory used by it. The execution flow and the data of the isolated application are safe
http://www.ibm.com/developerworks/po...-cellsecurity/
The Cell BE processor addresses this problem with its Runtime Secure Boot feature. It lets an application secure boot from the hardware an arbitrary number of times during runtime. Thus, even if other software in the system has been compromised in the past, a single application thread can still be robustly checked independently. In essence, the application can renew its trustworthiness as many times as needed even as the system stays running longer and gets more stale. Specifically, a hardware implemented authentication mechanism uses a hardware key to verify that the application has not been modified, and the authentication is based on a cryptographic algorithm.
This runtime secure boot, in fact, is tightly coupled with an SPE entering isolation mode
