MP129 Allowing the use of CNSA variant for ECDSA

Proposer David Rollason
Lead Analyst Piers Garton
Date raised 12/05/2020
StageRefinement Process
Implementation date Targeted for 04/11/2021 (Nov 21 SEC Release)
Latest update We will present the business requirements to the Working Group and the TABASC before requesting a DCC Preliminary Assessment.

What is the issue?

The Data Services Provider (DSP) considers itself to be a Remote Party in the context of SEC Schedule 8 ‘GB Companion Specification’ (GBCS) Section It therefore interpreted the GBCS as mandating the GCBS variant of Elliptic Curve Digital Signature Algorithm (ECDSA) for all device critical command signing operations, rather than the more common Commercial National Security Algorithm (CNSA) Suite variant, which is approved by the National Institute of Standards and Technology (NIST).

The Department for Business, Energy and Industrial Strategy (BEIS) advised that the DSP could have used the CNSA variant and remained compliant. The Smart Metering Key Infrastructure Policy Management Authority (SMKI PMA) also agreed that the above GBCS wording lacked clarity and would need to be updated to explicitly permit the use of CNSA by Remote Parties.

What is the solution?

The Proposed Solution is to make an amendment to the GB Companion Specification (GBCS) making it explicitly clear that Parties are permitted to use the Commercial National Security Algorithm (CNSA) variant for Critical Command signing.

Who is impacted?

No Parties are impacted.

What SEC documents are affected?

Schedule 8 'GB Companion Specification'


12 May 2020
Draft Proposal raised
19 Jun 2020
Converted to Modification Proposal
02 Sep 2020
Working Group meeting
19 Apr 2021
Discussed at Business Requirements Workshop

Modification documents

MP129 September 2020 Working Group Meeting summary
MP129 Modification Report v0.5
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