Paper
UC-Secure Star DKG for Non-Exportable Key Shares with VSS-Free Enforcement
Authors
Vipin Singh Sehrawat
Abstract
Distributed Key Generation (DKG) lets parties derive a common public key while keeping the signing key secret-shared. UC-secure DKG requires a verifiable-sharing enforcement layer -- classically satisfied via Verifiable Secret Sharing (VSS) and/or commitment-and-proof mechanisms -- for secrecy, uniqueness, and affine consistency. We target the Non-eXportable Key (NXK) setting enforced by hardware-backed key-isolation modules (e.g., TEEs, HSM-like APIs), formalized via an ideal KeyBox (keystore) functionality $\mathcal{F}_{KeyBox}$ that keeps shares non-exportable and permits only attested KeyBox-to-KeyBox sealing. With confidentiality delegated to the NXK boundary, the remaining challenge is enforcing transcript-defined affine consistency without exporting or resharing shares. State continuity rules out rewinding-based extraction, mandating straight-line techniques. We combine (i) KeyBox confidentiality; (ii) Unique Structure Verification (USV), a publicly verifiable certificate whose certified scalar never leaves the KeyBox yet whose public group element is transcript-derivable; and (iii) Fischlin-based UC-extractable NIZK arguments of knowledge in a gRO-CRP (global Random Oracle with Context-Restricted Programmability) model. We construct Star DKG (SDKG), a UC-secure scheme for multi-device threshold wallets where a designated service must co-sign but cannot sign alone, realizing a 1+1-out-of-$n$ star access structure (center plus any leaf) over roles (primary vs. recovery) with role-based device registration. In the $\mathcal{F}_{KeyBox}$-hybrid and gRO-CRP models, under DL and DDH assumptions with adaptive corruptions and secure erasures, SDKG UC-realizes a transcript-driven refinement of the standard UC-DKG functionality. Over a prime-order group of size $p$, SDKG incurs $\widetilde{O}(n\log p)$ communication overhead and $\widetilde{O}(n\log^{2.585}p)$ bit-operation cost.
Metadata
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Raw Data (Debug)
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"raw_xml": "<entry>\n <id>http://arxiv.org/abs/2602.22187v1</id>\n <title>UC-Secure Star DKG for Non-Exportable Key Shares with VSS-Free Enforcement</title>\n <updated>2026-02-25T18:32:42Z</updated>\n <link href='https://arxiv.org/abs/2602.22187v1' rel='alternate' type='text/html'/>\n <link href='https://arxiv.org/pdf/2602.22187v1' rel='related' title='pdf' type='application/pdf'/>\n <summary>Distributed Key Generation (DKG) lets parties derive a common public key while keeping the signing key secret-shared. UC-secure DKG requires a verifiable-sharing enforcement layer -- classically satisfied via Verifiable Secret Sharing (VSS) and/or commitment-and-proof mechanisms -- for secrecy, uniqueness, and affine consistency. We target the Non-eXportable Key (NXK) setting enforced by hardware-backed key-isolation modules (e.g., TEEs, HSM-like APIs), formalized via an ideal KeyBox (keystore) functionality $\\mathcal{F}_{KeyBox}$ that keeps shares non-exportable and permits only attested KeyBox-to-KeyBox sealing. With confidentiality delegated to the NXK boundary, the remaining challenge is enforcing transcript-defined affine consistency without exporting or resharing shares. State continuity rules out rewinding-based extraction, mandating straight-line techniques.\n We combine (i) KeyBox confidentiality; (ii) Unique Structure Verification (USV), a publicly verifiable certificate whose certified scalar never leaves the KeyBox yet whose public group element is transcript-derivable; and (iii) Fischlin-based UC-extractable NIZK arguments of knowledge in a gRO-CRP (global Random Oracle with Context-Restricted Programmability) model. We construct Star DKG (SDKG), a UC-secure scheme for multi-device threshold wallets where a designated service must co-sign but cannot sign alone, realizing a 1+1-out-of-$n$ star access structure (center plus any leaf) over roles (primary vs. recovery) with role-based device registration. In the $\\mathcal{F}_{KeyBox}$-hybrid and gRO-CRP models, under DL and DDH assumptions with adaptive corruptions and secure erasures, SDKG UC-realizes a transcript-driven refinement of the standard UC-DKG functionality. Over a prime-order group of size $p$, SDKG incurs $\\widetilde{O}(n\\log p)$ communication overhead and $\\widetilde{O}(n\\log^{2.585}p)$ bit-operation cost.</summary>\n <category scheme='http://arxiv.org/schemas/atom' term='cs.CR'/>\n <published>2026-02-25T18:32:42Z</published>\n <arxiv:primary_category term='cs.CR'/>\n <author>\n <name>Vipin Singh Sehrawat</name>\n </author>\n </entry>"
}