ISO/IEC 25706:2026

International
Standard
ISO/IEC 25706
First edition
Information technology — Security
2026-02
protocol and data model (SPDM)
collection
Reference number
© ISO/IEC 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO/IEC 2026 – All rights reserved
ii
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members
of ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
document should be noted (see www.iso.org/directives or www.iec.ch/members_experts/refdocs).
ISO and IEC draw attention to the possibility that the implementation of this document may involve the use of
(a) patent(s). ISO and IEC take no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO and IEC had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent database
available at www.iso.org/patents and https://patents.iec.ch. ISO and IEC shall not be held responsible for
identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by DMTF [as Security Protocol and Data Model (SPDM) Collection] and drafted
in accordance with its editorial rules. It was adopted, under the JTC 1 PAS procedure, by Joint Technical
Committee ISO/IEC JTC 1, Information technology.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html and www.iec.ch/national-
committees.
© ISO/IEC 2026 – All rights reserved
© ISO/IEC 2026 – All rights reserved
Security Protocol and Data Model (SPDM) Collection
CONTENTS
1 Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1 Security Protocol and Data Model (SPDM) Specification (DSP0274) . . . . . . . . . . . . . . . . . . . 10
2.2 SPDM over MCTP Binding Specification (DSP0275) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3 Secured Messages using SPDM over MCTP Binding Specification (DSP0276). . . . . . . . . . . 10
2.4 Secured Messages using SPDM Specification (DSP0277) . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.5 Advice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.1 Security Protocol and Data Model (SPDM) Specification (DSP0274) . . . . . . . . . . . . . . . . . . . 11
3.2 SPDM over MCTP Binding Specification (DSP0275) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3 Secured Messages using SPDM over MCTP Binding Specification (DSP0276). . . . . . . . . . . 11
3.4 Secured Messages using SPDM Specification (DSP0277) . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5 Terms and definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6 Symbols and abbreviated terms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7 Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.1 Document conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.2 Reserved and unassigned values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.3 Byte ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.3.1 Hash byte order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.3.2 Encoded ASN.1 byte order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.3.3 Octet string byte order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.3.4 Signature byte order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.3.4.1 ECDSA signatures byte order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.3.4.2 SM2 signatures byte order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.4 Sizes and lengths. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7.5 SPDM data type conventions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7.5.1 SPDM data types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7.5.2 Integers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7.6 Version encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7.7 Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.8 Text or string encoding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
7.9 Deprecated material. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.10 Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8 Security Protocol and Data Model (SPDM) Specification (DSP0274) . . . . . . . . . . . . . . . . . . . . . . . 26
8.1 SPDM message exchanges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.1.1 Security capability discovery and negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.1.2 Identity authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.1.2.1 Identity provisioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
8.1.2.1.1 Certificate models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
8.1.2.2 Raw public keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.1.2.3 Runtime authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.1.3 Firmware and configuration measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.1.4 Secure sessions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
© ISO/IEC 2026 – All rights reserved
Version 1.0.0 Published 3
Security Protocol and Data Model (SPDM) Collection
8.1.5 Mutual authentication overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.1.6 Multiple asymmetric key support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.1.7 Custom environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.1.8 Notification overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.2 SPDM messaging protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.2.1 SPDM connection model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.2.2 SPDM bits-to-bytes mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.2.3 Generic SPDM message format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
8.2.3.1 SPDM version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
8.2.4 SPDM request codes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
8.2.5 SPDM response codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
8.2.6 SPDM request and response code issuance allowance . . . . . . . . . . . . . . . . . . . . . . . . . 39
8.2.7 Concurrent SPDM message processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.2.8 Requirements for Requesters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.2.9 Requirements for Responders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.2.10 Transcript and transcript hash calculation rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
8.3 Timing requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
8.3.1 Timing measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
8.3.2 Timing parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
8.3.3 Timing specification table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
8.4 SPDM messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.4.1 Capability discovery and negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.4.1.1 Negotiated state preamble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
8.4.2GET_VERSION request andVERSION response messages . . . . . . . . . . . . . . . . . . . . . . 46
8.4.3GET_CAPABILITIES request andCAPABILITIES response messages . . . . . . . . . . . 49
8.4.3.1 Supported algorithms block. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
8.4.4NEGOTIATE_ALGORITHMS request andALGORITHMS response messages . . . . . . . . . 58
8.4.4.1 Connection behavior after VCA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
8.4.4.2 Multiple asymmetric key negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
8.4.4.3 Multiple asymmetric key use for Responder authentication . . . . . . . . . . . . . . . . . . 71
8.4.4.4 Multiple asymmetric key use for Requester authentication. . . . . . . . . . . . . . . . . . . 71
8.4.4.5 Multiple asymmetric key connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
8.4.5 Responder identity authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
8.4.6 Requester identity authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
8.4.6.1 Certificates and certificate chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
8.4.7GET_DIGESTS request andDIGESTS response messages . . . . . . . . . . . . . . . . . . . . . . 75
8.4.8GET_CERTIFICATE request andCERTIFICATE response messages . . . . . . . . . . . . . 79
8.4.8.1 Mutual authentication requirements forGET_CERTIFICATE andCERTIFICATE
messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
8.4.8.2 SPDM certificate requirements and recommendations. . . . . . . . . . . . . . . . . . . . . . 81
8.4.8.2.1 Extended Key Usage authentication OIDs . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
8.4.8.2.2 SPDM Non-Critical Certificate Extension OID . . . . . . . . . . . . . . . . . . . . . . . . 84
8.4.9CHALLENGE request andCHALLENGE_AUTH response messages. . . . . . . . . . . . . . . . . 85
8.4.9.1CHALLENGE_AUTH signature generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
8.4.9.2CHALLENGE_AUTH signature verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
8.4.9.2.1 Request ordering and message transcript computation rules for M1 and
© ISO/IEC 2026 – All rights reserved
4 Published Version 1.0.0
Security Protocol and Data Model (SPDM) Collection
M2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
8.4.9.3 Basic mutual authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
8.4.9.3.1 Mutual authentication message transcript . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
8.4.10 Firmware and other measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
8.4.11GET_MEASUREMENTS request andMEASUREMENTS response messages . . . . . . . . . . 95
8.4.11.1 Measurement block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
8.4.11.1.1 DMTF specification for the Measurement field of a measurement block . . 101
8.4.11.1.2 Device mode field of a measurement block . . . . . . . . . . . . . . . . . . . . . . . . 103
8.4.11.1.3 Manifest format for a measurement block. . . . . . . . . . . . . . . . . . . . . . . . . . 104
8.4.11.2MEASUREMENTS signature generation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
8.4.11.3MEASUREMENTS signature verification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
8.4.12ERROR response message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
8.4.12.1 Standards body or vendor-defined header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
8.4.13RESPOND_IF_READY request message format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
8.4.14VENDOR_DEFINED_REQUEST request message. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
8.4.15VENDOR_DEFINED_RESPONSE response message . . . . . . . . . . . . . . . . . . . . . . . . . . 114
8.4.15.1 VendorDefinedReqPayload and VendorDefinedRespPayload defined by DMTF
specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
8.4.16KEY_EXCHANGE request andKEY_EXCHANGE_RSP response messages . . . . . . . . . 115
8.4.16.1 Session-based mutual authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
8.4.16.1.1 Specify Requester certificate for session-based mutual authentication . . . 123
8.4.17FINISH request andFINISH_RSP response messages . . . . . . . . . . . . . . . . . . . . . . 124
8.4.17.1 Transcript and transcript hash calculation rules forKEY_EXCHANGE . . . . . . . . . 125
8.4.18PSK_EXCHANGE request andPSK_EXCHANGE_RSP response messages . . . . . . . . . 128
8.4.19PSK_FINISH request andPSK_FINISH_RSP response messages. . . . . . . . . . . . . . 135
8.4.20HEARTBEAT request andHEARTBEAT_ACK response messages. . . . . . . . . . . . . . . . 136
8.4.20.1 Heartbeat additional information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
8.4.21KEY_UPDATE request andKEY_UPDATE_ACK response messages. . . . . . . . . . . . . . 137
8.4.21.1 Session key update synchronization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
8.4.21.2KEY_UPDATE transport allowances. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
8.4.22GET_ENCAPSULATED_REQUEST request andENCAPSULATED_REQUEST response
messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
8.4.22.1 Encapsulated request flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
8.4.22.2 Optimized encapsulated request flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
8.4.22.3 TriggeringGET_ENCAPSULATED_REQUEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
8.4.22.4 Additional constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
8.4.23DELIVER_ENCAPSULATED_RESPONSE request andENCAPSULATED_RESPONSE_ACK
response messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
8.4.23.1 Additional information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
8.4.23.2 Allowance for encapsulated requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
8.4.23.3 Certain error handling in encapsulated flows . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
8.4.23.3.1 Response not ready . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
8.4.23.3.2 Timeouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
8.4.24END_SESSION request andEND_SESSION_ACK response messages . . . . . . . . . . . 151
8.4.25 Certificate provisioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
8.4.25.1GET_CSR request and CSR response messages . . . . . . . . . . . . . . . . . . . . . . . . 153
© ISO/IEC 2026 – All rights reserved
Version 1.0.0 Published 5
Security Protocol and Data Model (SPDM) Collection
8.4.25.2SET_CERTIFICATE request andSET_CERTIFICATE_RSP response
messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
8.4.26 Large SPDM message transfer mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
8.4.26.1CHUNK_SEND request andCHUNK_SEND_ACK response message . . . . . . . . . . 158
8.4.26.2CHUNK_GET request andCHUNK_RESPONSE response message . . . . . . . . . . . 161
8.4.26.3 Additional chunk transfer requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
8.4.27 Key configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
8.4.27.1GET_KEY_PAIR_INFO request andKEY_PAIR_INFO response. . . . . . . . . . . . 165
8.4.27.2SET_KEY_PAIR_INFO request andSET_KEY_PAIR_INFO_ACK response . . . 168
8.4.27.3 Key pair ID modification error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
8.4.28 Event mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
8.4.28.1GET_SUPPORTED_EVENT_TYPES request andSUPPORTED_EVENT_TYPES
response message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
8.4.28.1.1 Event group format additional information . . . . . . . . . . . . . . . . . . . . . . . . . 174
8.4.28.2SUBSCRIBE_EVENT_TYPES request andSUBSCRIBE_EVENT_TYPES_ACK
response message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
8.4.28.2.1 Additional subscription list information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
8.4.28.3SEND_EVENT request andEVENT_ACK response message. . . . . . . . . . . . . . . . 176
8.4.28.4 Event Instance ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
8.4.29GET_ENDPOINT_INFO request andENDPOINT_INFO response messages . . . . . . . 178
8.4.29.1ENDPOINT_INFO signature generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
8.4.29.2ENDPOINT_INFO signature verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
8.4.30 Measurement extension log mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
8.4.30.1GET_MEASUREMENT_EXTENSION_LOG request and
MEASUREMENT_EXTENSION_LOG response messages . . . . . . . . . . . . . . . . . . . . . . . . . . 183
8.4.30.2 DMTF Measurement Extension Log Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
8.4.30.3 Example: Verifying Measurement Extension Log Against Hash-Extend
Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
8.5 Session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
8.5.1 Session handshake phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
8.5.2 Application phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
8.5.3 Session termination phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
8.5.4 Simultaneous active sessions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
8.5.5 Records and session ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
8.6 Key schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
8.6.1 DHE secret computation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
8.6.2 Transcript hash in key derivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
8.6.3 TH1 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
8.6.4 TH2 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
8.6.5 Key schedule major secrets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
8.6.5.1 Request-direction handshake secret. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
8.6.5.2 Response-direction handshake secret . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
8.6.5.3 Request-direction data secret . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
8.6.5.4 Response-direction data secret . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
8.6.6 Encryption key and IV derivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
8.6.7 finished_key derivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
© ISO/IEC 2026 – All rights reserved
6 Published Version 1.0.0
Security Protocol and Data Model (SPDM) Collection
8.6.8 Deriving additional keys from the Export Master Secret . . . . . . . . . . . . . . . . . . . . . . . . 195
8.6.9 Major secrets update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
8.7 Application data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
8.7.1 Nonce derivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
8.8 General opaque data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
8.9 Signature generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
8.9.1 Signing algorithms in extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
8.9.2 RSA and ECDSA signing algorithms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
8.9.3 EdDSA signing algorithms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
8.9.3.1 Ed25519 sign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
8.9.3.2 Ed448 sign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
8.9.4 SM2 signing algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
8.9.5 Signature algorithm references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
8.10 Signature verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
8.10.1 Signature verification algorithms in extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
8.10.2 RSA and ECDSA signature verification algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
8.10.3 EdDSA signature verification algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
8.10.3.1 Ed25519 verify . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
8.10.3.2 Ed448 verify . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
8.10.4 SM2 signature verification algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
8.11 General ordering rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
8.12 DMTF event types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
8.12.1 Event type details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
8.12.1.1 Event Lost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
8.12.1.2 Measurement changed event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
8.12.1.3 Measurement pre-update event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
8.12.1.4 Certificate changed event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
9 SPDM over MCTP Binding Specification (DSP0275). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
9.0.1 SPDM over MCTP binding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
9.0.1.1 SPDM over MCTP message fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
9.0.1.2 Requester and responder tracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
9.0.2 Message tracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
9.0.3 Version reporting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
10 Secured Messages using SPDM over MCTP Binding Specification (DSP0276) . . . . . . . . . . . . . 208
10.1 Secured messages over MCTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
10.1.1 Sequence number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
10.1.2 MCTP encapsulated format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
10.2 Transport requirements or allowances. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
10.2.1 Transmission retries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
10.2.2 Certain SPDM message allowances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
10.2.3 Version reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
10.2.4 Key management during key update. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
10.3 Timing requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
11 Secured Messages using SPDM Specification (DSP0277) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
11.1 Secured Message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
11.1.1 Secured Message format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
11.1.2 Secured Message protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
© ISO/IEC 2026 – All rights reserved
Version 1.0.0 Published 7
Security Protocol and Data Model (SPDM) Collection
11.1.2.1 AEAD encryption keys and other secrets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
11.1.2.2 AEAD requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
11.1.2.2.1 Message Authentication Only session . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
11.1.2.2.2 Encryption and Message Authentication session . . . . . . . . . . . . . . . . . . . . 215
11.1.2.3 Per-message nonce derivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
11.1.2.3.1 Other per-message nonce requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 216
11.1.2.4 Encryption requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
11.2 Compatibility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
11.3 Version support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
11.3.1 Version selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
11.4 Transport requirements or allowances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
11.4.1 Transmission reliability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
11.4.2 Certain SPDM message allowances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
11.4.3ERROR response message allowances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
11.4.4 Key update allowances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
11.5 Secured Messages opaque data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
11.5.1 Secured Message opaque element data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
11.5.1.1 Version selection data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
11.5.1.2 Supported version list data format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
11.6 SPDM general opaque data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
12 ANNEX A (informative) TLS 1.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
13 ANNEX B (informative) Device certificate example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
14 ANNEX C (informative) OID reference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
15 ANNEX D (informative) Variable name reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
16 ANNEX E (informative) Sequence number layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
17 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
© ISO/IEC 2026 – All rights reserved
8 Published Version 1.0.0
Security Protocol and Data Model (SPDM) Collection
1 Foreword
The Security Protocols and Data Models (SPDM) Working Group of DMTF prepared the Security Protocol and
Data Model (SPDM) Specification (DSP0274).
The Platform Management Communications Infrastructure (PMCI) Working Group of DMTF prepared the
Security Protocol and Data Model (SPDM) over MCTP Binding Specification (DSP0275), the Secured Messages
using SPDM over MCTP Binding Specification (DSP0276), and the Secured Messages using SPDM
Specification (DSP0277).
DMTF is a not-for-profit association of industry members that promotes enterprise and systems management
and interoperability. For information about DMTF, see https://www.dmtf.org.
Table 1 — Component documents lists the specifications that this collection contains.
Table 1 — Component documents
Document number Document title Version
DSP0274 Security Protocol and Data Model (SPDM) Specification 1.3.1
DSP0275 Security Protocol and Data Model (SPDM) over MCTP Binding Specification 1.0.2
DSP0276 Secured Messages using SPDM over MCTP Binding Specification 1.2.0
DSP0277 Secured Messages using SPDM Specification 1.2.0
© ISO/IEC 2026 – All rights reserved
Version 1.0.0 Published 9
Security Protocol and Data Model (SPDM) Collection
2 Introduction
2.1 Security Protocol and Data Model (SPDM) Specification (DSP0274)
DSP0274 defines messages, data objects, and sequences for performing message exchanges over a variety of
transport and physical media. The description of message exchanges includes authentication and provisioning of
hardware identities, measurement for firmware identities, session key exchange protocols to enable
confidentiality with integrity-protected data communication, and other related capabilities. SPDM enables efficient
access to low-level security capabilities and operations. In addition, other mechanisms, including non-DMTF-
defined mechanisms, can use the SPDM.
2.2 SPDM over MCTP Binding Specification (DSP0275)
DSP0275 defines how SPDM is transported over MCTP communications. SPDM is supported as a message
type over MCTP, and the SPDM over MCTP binding defines the format of SPDM messages transported over
MCTP.
2.3 Secured Messages using SPDM over MCTP Binding Specification
(DSP0276)
DSP0276 binds Secured Messages using the SPDM specification (DSP0277) to MCTP transport.
2.4 Secured Messages using SPDM Specification (DSP0277)
DSP0277 defines the methodology that various PMCI transports can use to communicate various application
data securely by utilizing SPDM. Specifically, DSP0277 defines the transport requirements for SPDM records,
which form the basis of encryption and message authentication. Furthermore, DSP0277 contains guidance and
certain decisions that it defers to the binding specification, which binds Secured Messages to a specific transport.
Thus, the binding specification is expected to finalize those decisions or guidance by way of normalization or
recommendation. DSP0277 was written with PMCI transports in mind, but nothing precludes specifying bindings
to other transports.
2.5 Advice
The authors of these specifications recommend that readers visit tutorial and educational materials under
Security Protocols and Data Models (SPDM) and Platform Management Communications Infrastructure (PMCI)
on the DMTF website prior to or during the reading of these specifications to aid in understanding them fully.
© ISO/IEC 2026 – All rights reserved
10 Published Version 1.0.0
Security Protocol and Data Model (SPDM) Collection
3 Scope
3.1 Security Protocol and Data Model (SPDM) Specification (DSP0274)
DSP0274 describes how to use messages, data objects, and sequences to exchange messages between two
devices over a variety of transports and physical media. DSP0274 contains the message exchanges, sequence
diagrams, message formats, and other relevant semantics for such message exchanges, including
authentication of hardware identities and firmware measurements.
Other specifications define the mapping of these messages to different transports and physical media. DSP0274
provides information to enable security policy enforcement but does not specify individual policy decisions.
3.2 SPDM over MCTP Binding Specification (DSP0275)
DSP0275 defines the format of Security Protocol and Data Model (SPDM) over MCTP messages. DSP0275
describes both SPDM over MCTP binding and the common format for SPDM over MCTP messages.
3.3 Secured Messages using SPDM over MCTP Binding Specification
(DSP0276)
DSP0276 binds Secured Messages using SPDM to MCTP transport and further defines the transport specific
details as outlined in Secured Messages using SPDM Specification (DSP0277). DSP0276 1.2.0 (this version)
binds to version 1.2.0 and all 1.2 errata versions of DSP0277.
3.4 Secured Messages using SPDM Specification (DSP0277)
DSP0277 defines a generic record format used to encrypt and authenticate any application data within SPDM’s
secure session. Also, relating to encryption, message authentication, and secure sessions, DSP0277 further
defines those areas in SPDM that the specification states are the responsibilities of the transport layer. DSP0277
requires SPDM version 1.1 or later.
© ISO/IEC 2026 – All rights reserved
Version 1.0.0 Published 11
Security Protocol and Data Model (SPDM) Collection
4 Normative references
The following referenced documents are indispensable for the application of the specifications in this collection.
For dated or versioned references, only the edition cited, including any corrigenda or DMTF update versions,
applies. For references without date or version, the latest published edition of the referenced document, including
any corrigenda or DMTF update versions, applies.
• DMTF DSP0004, Common Information Model (CIM) Metamodel, https://www.dmtf.org/sites/default/files/
standards/documents/DSP0004_3.0.pdf
• DMTF DSP0223, Generic Operations, https://www.dmtf.org/sites/default/files/standards/documents/
DSP0223_1.0.pdf
• DMTF DSP0236, MCTP Base Specification 1.3, https://www.dmtf.org/sites/default/files/standards/
documents/DSP0236_1.3.pdf
• DMTF DSP0239, MCTP IDs and Codes 1.7, https://www.dmtf.org/sites/default/files/standards/documents/
DSP0239_1.7.pdf
• DMTF DSP0240, Platform Level Data Model (PLDM) Base Specification, https://www.dmtf.org/sites/default/
files/standards/documents/DSP0240_1.0.pdf
• DMTF DSP0274, Security Protocol and Data Model (SPDM) Specification, https://www.dmtf.org/dsp/
DSP0274
• DMTF DSP0275, Security Protocol and Data Model (SPDM) over MCTP Binding Specification,
https://www.dmtf.org/dsp/DSP0275
• DMTF DSP0276, Secured Messages using SPDM over MCTP Binding Specification, https://www.dmtf.org/
dsp/DSP0276
• DMTF DSP0277, Secured Messages using SPDM Specification, https://www.dmtf.org/dsp/DSP0277
• DMTF DSP1001, Management Profile Usage Guide, https://www.dmtf.org/sites/default/files/standards/
documents/DSP1001_1.2.pdf
• GB/T 32905-2016, Information security technology—SM3 cryptographic hash algorithm, August 2016
• GB/T 32907-2016, Information security technology—SM4 block cipher algorithm, August 2016
• GB/T 32918.1-2016, Information security technology—Public key cryptographic algorithm SM2 based on
elliptic curves—Part 1: General, August 2016
• GB/T 32918.2-2016, Information security technology—Public key cryptographic algorithm SM2 based on
elliptic curves—Part 2: Digital signature algorithm, August 2016
• GB/T 32918.3-2016, Information security technology—Public key cryptographic algorithm SM2 based on
elliptic curves—Part 3: Key exchange protocol, August 2016
• GB/T 32918.4-2016, Information security technology—Public key cryptographic algorithm SM2 based on
elliptic curves—Part 4: Public key encryption algorithm, August 2016
• GB/T 32918.5-2016, Information security technology—Public key cryptographic algorithm SM2 based on
elliptic curves—Part 5: Parameter definition, August 2016
• IETF RFC 2986, PKCS #10: Certification Request Syntax Specification, November 2000,
https://tools.ietf.org/html/rfc2986
• IETF RFC 4716, The Secure Shell (SSH) Public Key File Format, November 2006, https://tools.ietf.org/html/
rfc4716
• IETF RFC 5116, An Interface and Algorithms for Authenticated Encryption, January 2008,
© ISO/IEC 2026 – All rights reserved
12 Published Version 1.0.0
Security Protocol and Data Model (SPDM) Collection
https://tools.ietf.org/html/rfc5116
• IETF RFC 5234, Augmented BNF for Syntax Specifications: ABNF, January 2008, https://tools.ietf.org/html/
rfc5234
• IETF RFC 5280, Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL)
Profile, May 2008, https://tools.ietf.org/html/rfc5280
• IETF RFC 7250, Using Raw Public Keys in Transport Layer Security (TLS) and Datagram Transport Layer
Security (DTLS), June 2014, https://tools.ietf.org/html/rfc7250
• IETF RFC 7919, Negotiated Finite Field Diffie-Hellman Ephemeral Parameters for Transport Layer Security
(TLS), August 2016, https://tools.ietf.org/html/rfc7
...