From I bet you didn’t know this department
Ctrl-alt-del, the three finger salute has an official name. It’s SAS or “Secure Attention Sequence”.
I learned that from Microsoft’s Tablet PC site.
C1. A Tablet PC without an attached keyboard must support a single, dedicated, non-overloaded hardware mechanism for generating the Secure Attention Sequence (SAS), also known as "CTRL+ALT+DEL" or "CAD."
C2. If the SAS button is implemented as a Human Interface Device (HID), the HID-compliant button driver must provide a keyboard collection to report the SAS event.