Tor.Us is an open source project that did distributed key generation, distributed key management, and logins via open auth. In these Medium articles they cover the fundamentals of their distributed key generation and management.

Recently it was announced that has raised $13M and rebranded to web3auth (Coindesk Jan 12 2022 Torus Rebrands to Web3Auth)

What Distributed Key Generation Is
How Torus Works — Part 1
Key Assignments, Resolution and Retrieval
How Torus Works — Part 2