NIST requests comments on IR 8214B initial public draft: Notes on Threshold EdDSA/Schnorr Signatures
August 12, 2022

NIST requests public comments on the initial public draft (ipd) of NIST IR 8214B, Notes on Threshold EdDSA/Schnorr Signatures. This report considers signature schemes that are compatible with the verification phase of the Edwards Curve Digital Signature Algorithm (EdDSA) specified in Draft Federal Information Processing Standards (FIPS) publication 186-5. The report analyzes threshold schemes, where the private signing key is secret-shared across multiple parties, and signatures can be produced without the parties reconstructing the key. Security holds even if up to a threshold number of parties has been compromised.

The report reviews the properties of EdDSA/Schnorr deterministic and probabilistic signatures schemes, both in the conventional (non-threshold) and threshold setting, summarizing various known properties and approaches. These threshold signatures can allow for a drop-in replacement of conventional signatures without changing the legacy code used for verification. This work is useful to advance the NIST Multi-Party Threshold Cryptography project, which is also interested in other primitives. The document suggests that it is beneficial to further consult with the community of experts for security formulations, technical descriptions, and reference implementations. 

The report includes a section for each of the following: 

• Conventional setting: gives context of conventional EdDSA/Schnorr-style signature schemes and their security properties; 
• Threshold approaches: summarizes various threshold approaches for deterministic and probabilistic schemes, at a high level; 
• Further considerations: describes how various aspects only arise in the threshold setting, thus requiring a more sophisticated analysis with respect to the security formulation; 
• Conclusions: identifies the need for additional analysis aided by the community of experts. 

The public comment period is open through October 24, 2022. See the publication details for a copy of the draft and instructions for submitting comments. 

NOTE: A call for patent claims is included on page iii of this draft. For additional information, see the Information Technology Laboratory (ITL) Patent Policy – Inclusion of Patents in ITL Publications.