Signature-Agnostic MPC Custody Survives the Post-Quantum Break of Threshold Signatures

arXiv·medium signal

Digital-asset custody has relied on threshold signature schemes (TSS) so that t-of-n parties must approve any operation, but the post-quantum transition disrupts this: standardized hash-based signatures resist efficient threshold signing and lattice-based threshold protocols remain immature. This work presents threshold authorization without threshold signatures — a signature-agnostic MPC custody design that preserves t-of-n approval independent of the underlying signature scheme. Timely for teams planning PQC migrations of custody or key-management systems.