Manifesting Unobtainable Secrets: Threshold Elliptic Curve Key Generation using Nested Shamir Secret Sharing
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We present a mechanism to manifest unobtainable secrets using a nested Shamir secret sharing scheme to create public/private key pairs for elliptic curves. A threshold secret sharing scheme can be used as a decentralised trust mechanism with applications in identity validation, message decryption, and agreement empowerment. Decentralising trust means that there is no single point vulnerability which could enable compromise of a system. Our primary interest is in twisted Edwards curves as used in EdDSA, and the related Diffie-Hellman key-exchange algorithms. The key generation is also decentralised, so can be used as a decentralised secret RNG suitable for use in other algorithms. The algorithms presented could be used to fill a “[TBS]” in the draft IETF specification “Threshold modes in elliptic curves” published in 2020 and updated in 2022.
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