Identifiable Cheating Entity Flexible Round-Optimized Schnorr Threshold (ICE FROST) Signature Protocol

This paper presents an Identi able Cheating Entity (ICE) FROST signature protocol that is an improvement over the FROST signature scheme (Komlo and Goldberg, SAC 2020) since it can identify cheating participants in its Key Generation protocol. The proposed threshold signature protocol achieves robustness in the Key Generation phase of the threshold signature protocol by introducing a cheating identi cation mechanism and then excluding cheating participants from the protocol. By enabling the cheating identi cation mechanism, we remove the need to abort the Key Generation protocol every time cheating activity is suspected. Our cheating identi cation mechanism allows every participant to individually check the validity of complaints issued against possibly cheating participants. Then, after all of the cheating participants are eliminated, the Key Generation protocol is guaranteed to nish successfully. On the other hand, the signing process only achieves a weak form of robustness, as in the original FROST. We then introduce static public key variant of ICE FROST. Our work is the rst to consider static private/public keys for a round-optimized Schnorr-based signature scheme. With static public keys, the group's established public and private keys remain constant for the lifetime of signers, while the signing shares of each participant are updated over time, as well as the set of group members, which ensures the long-term security of the static keys and facilitates the veri cation process of the generated threshold signature because a group of signers communicates their public key to the veri er only once during the group's lifetime. Our implementation benchmarks demonstrate that the runtime of the protocol is feasible for real-world applications.