RPMC Support Using eSPI OOB (eRPMC)

Architecture Specification

ID Date Version Classification
739180 06/01/2025 Public
Document Table of Contents
Document Table of Contents
Legal Revision History References Introduction eRPMC Implementation
Legal
Revision History
References
Introduction
eRPMC Implementation
eRPMC Implementation eRPMC - RPMC Commands as OOB over eSPI (Tunneled SMBus Messages – MCTP) Maximum Payload Size (MPS) SMB/MCTP Parameters RPMC Commands Reserved Command-type Monotonic Counters
eRPMC - RPMC Commands as OOB over eSPI (Tunneled SMBus Messages – MCTP)
eRPMC - RPMC Commands as OOB over eSPI (Tunneled SMBus Messages – MCTP) Format Used for RPMC OOB Commands
Format Used for RPMC OOB Commands
Maximum Payload Size (MPS)
SMB/MCTP Parameters
RPMC Commands
RPMC Commands Write Root Key Register Update HMAC Key Register Increment Monotonic Counter Request Monotonic Counter Read RPMC Parameters
Write Root Key Register
Update HMAC Key Register
Increment Monotonic Counter
Request Monotonic Counter
Read RPMC Parameters
Reserved Command-type
Monotonic Counters

Introduction

RPMC functionality is defined in Intel Serial Flash Hardening Product External Architecture Specification (EAS) Revision 0.7 (document link).

Certain types of attacks can be detected by using monotonic counter values in the platform. RPMC implements authenticated commands to the protected monotonic counters.

Adhering to the above RPMC specification, this document outlines Firmware support for RPMC implemented in an Embedded Controller (EC device) over eSPI as Out-Of-Band (OOB) authenticated messages.

EC device must meet all the associated HW requirements for RPMC providing the necessary authentication and secure internal nonvolatile storage for RPMC keys and counters.

EC firmware must be cryptographically signed and serve as the Root of Trust (RoT), ensuring its integrity and authenticity through a secure boot process and verified firmware updates

eRPMC Implementation