tBLS: Threshold BLS Signature Scheme

"Preview Talk" (by Team BDLR) @ MPTS 2026, in reply to the NIST Threshold Call

Abstract. In this presentation, I will talk about tBLS, a non-interactive (t, n)-threshold variant of the classic Boneh-Lynn-Shacham (BLS) signature scheme. The construction distributes signing capability among n parties such that any subset of at least 𝑡+1 participants can jointly produce a single compact signature, while preserving the verification interface, encodings, and compatibility of standard single-party BLS signatures. Partial signatures are generated non-interactively, are publicly verifiable, and are combined deterministically using Lagrange interpolation in the exponent, yielding a unique final signature indistinguishable from a standard BLS signature.

Joint work: Renas Bacho, Alexandra Boldyreva, Sourav Das, Julian Loss.

[Slides] Suggested readings:

• Preview Writeup: tBLS: Threshold BLS Signature Scheme
• On the Adaptive Security of the Threshold BLS Signature Scheme (ia.cr/2022/534)