"Preview Talk" (by team Octopus) @ TCPT3, in reply to the NIST Threshold Call
Abstract: In this talk, we present three threshold ECDSA schemes — a two-party protocol and two t-out-of-n threshold signature protocols — submitted as the Octopus team's preview proposals to the NIST Multi-Party Threshold Cryptography (MPTC) call. All three schemes run in three rounds. (1) Our two-party scheme, Menshen, requires only a single multiplicative-to-additive (MtA) conversion, also known as oblivious linear evaluation (OLE); importantly, this MtA is key-independent. (2) Our first t-out-of-n scheme, Octopus-CL, relies on standard Castagnos–Laguillaumie (CL) encryption. It provides cheater identification for any threshold t, and additionally guarantees robustness in the honest-majority setting. (3) Our second t-out-of-n scheme, Octopus-TCL, builds on a threshold version of CL encryption.
Joint work: Man Ho Au, Robert H. Deng, Liming Gao, Bowen Jiang, Xianhui Lu, Tian Qiu, Guofeng Tang, Ruida Wang, Haiyang Xue, Guomin Yang, Chengru Zhang.
Suggested readings
- Preview Writeup (PDF): Menshen and Octopus-(T)CL: Two-party and Threshold ECDSA Schemes
- Efficient online-friendly two-party ECDSA signature (ia.cr/2022/318)
- Robust Threshold ECDSA with Online-Friendly Design in Three Rounds (ia.cr/2025/910)
- Three-Round (Robust) Threshold ECDSA from Threshold CL Encryption (ia.cr/2026/190)
