Honest-Majority Threshold ECDSA with Batch Generation of Key-Independent Presignatures

Several protocols have been proposed recently for threshold ECDSA signatures, mostly in the dishonest-majority setting. Yet in so-called key-management networks, where a fixed set of servers share a large number of keys on behalf of multiple users, it may be reasonable to assume that a majority of the servers remain uncompromised, and in that case there may be several advantages to using an honest-majority protocol. With this in mind, we describe an efficient protocol for actively secure, honest-majority threshold ECDSA supporting batch generation of key-independent presignatures that allow for “non-interactive” online signing; these properties are not available in existing dishonest-majority protocols. Our protocol offers low latency and high throughput, and runs at an amortized rate of roughly 1.3 ms per presignature (after which signatures can be generated in less than 100 microseconds).