RPMC Support Using eSPI OOB (eRPMC)

Architecture Specification

ID Date Version Classification
739180 02/01/2025 Public

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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

Maximum Payload Size (MPS)

The EC device supports an OOB MPS of 64 bytes (73 bytes for MCTP, refer Ref [2]). This requires any OOB message with an MCTP payload size greater than 64 bytes to be broken up into two messages.

Note:An expansion of the signature field for an extension of the RPMC standard to SHA-384 will also require several commands to be broken up into two messages.
SMB/MCTP Parameters