Microsoft Technology Licensing, LLC

Varun Gandhi

Alastair Wolman

Stefan Saroiu

Landon Prentice Cox

A health ticket minting process operates in a secure enclave on a computing device to ensure liveness of the enclave should a maliciously-compromised operating system deny service to starve the enclave. Cryptographically-secured health tickets provided by the minting process reset an authenticated watchdog timer (AWDT) that reboots the device from a hardware-protected recovery operating system if the timer expires. The health tickets are written to a secure channel using a symmetric key that is provisioned by repurposing an existing Intel SGX (Software Guard Extension) Versioning Support protocol that enables migration of secrets between enclaves that have the same author. In the event that the enclave fails to make forward progress and health tickets are not minted, then the AWDT expires and forces the reboot and re-imaging to a known good state to evict the malware from the computing device.

Liveness guarantees in secure enclaves using health tickets

Cryptographically-secured deferral tickets provided by a minting process that runs in a secure enclave on a computing device reset an authenticated watchdog timer that reboots the device from a hardware-protected recovery operating system to re-image the device into a known good state if the timer expires. The deferral tickets are written to a secure channel using a symmetric key that is provisioned by repurposing an existing Intel SGX (Software Guard Extension) Versioning Support protocol that enables migration of secrets between enclaves that have the same author. In an illustrative embodiment, the deferral ticket minting process and authenticated watchdog timer execute locally to enable automated recovery of the computing device when utilized in far edge infrastructure of a fifth generation (5G) network such as a distributed unit (DU) of a radio access network (RAN).

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Varun Gandhi