`mithril-signer`: State Machine Flow, KES Period, and Safe Registration

Why I Studied mithril-signer After contributing to the Mithril project and reading the client/aggregator modules, I realized that the signer is one of the most critical components in the whole protocol. The signer is operated by stake pool operators (SPOs) and is responsible for producing the individual signatures that the aggregator later combines into a Mithril certificate. If signers crash or register incorrect data, then participation drops and certificate production can become slow or unstable. So understanding the signer is not only “reading code,” but understanding the real operational reliability of Mithril. In this post, I summarize how mithril-signer works from an engineer’s point of view: the state machine (status) flow, how registration and signing rounds work, what kind of data moves between signer and aggregator, and why KES period handling is a correctness-sensitive part of registration. What the Signer Does (High-level Responsibility) You can think of the signer as a lo