Paper 2026/400 Original: eprint.iacr.org/2026/400 ↗

Non-interactive Blind Signatures with Threshold Issuance

Abstract

Non-interactive blind signatures (NIBS) capture the minimal setting of blind signatures where the message space is restricted to unstructured random strings. They enable a signer to pre-compute presignatures without prior interaction, while ensuring that only the intended recipient can derive the corresponding blind signature. In this work, we consider the problem of threshold issuance of NIBS. Specifically, we introduce the notion of non-interactive threshold blind signatures (NITBS), where a user obtains partial presignatures from a threshold of signers and locally combines them into a valid blind signature. We provide a formal treatment of this primitive by defining the corresponding security notions of blindness and one-more unforgeability. We then present the first concrete construction of NITBS, obtained by adapting the Pointcheval-Sanders (PS) signature scheme, and establish its security in the algebraic group model. Our micro-benchmarking results show that our construction attains the smallest presignature and signature sizes and the fastest issuance among all existing NIBS schemes.