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Mithril Signer Configuration

The Mithril signer is the component that signs snapshots of the blockchain state. It runs on the block producer because it needs access to the pool's operational certificate and KES secret key, which it uses to compute your PoolId, prove pool ownership, and participate in the multi-signature process.

important

The Mithril signer must never connect directly to the internet. In the production deployment (required on mainnet), all outbound traffic goes exclusively through the Mithril relay. See Setting up a Mithril relay for more details.

Overview​

Setting up the signer involves four stages:

  1. Prerequisites -- ensure the Cardano node is fully synchronized and running a compatible version, with active KES keys. The signer requires read access to the node's database directory and read/write access to the node socket.
  2. Installation -- download the pre-built mithril-signer binary or build it from source, then register it as a systemd service running as the same user as the Cardano node.
  3. Credential configuration -- create an environment file at /opt/mithril/mithril-signer.env pointing to your KES secret key, operational certificate, Cardano node database, node socket, and cardano-cli path.
  4. Connecting the pipeline -- set the RELAY_ENDPOINT variable to your internal Mithril relay address (for example, http://192.168.1.50:3132). The signer sends signatures through the relay, which forwards them to the Mithril aggregator.

Key operational details​

  • The signer is lightweight: less than 5% CPU and under 200 MB of memory during normal operation
  • It sends a new signature roughly every 10 minutes and a new registration every 5 days
  • On first launch, a pre-loading phase runs with higher CPU usage for approximately 5 hours
  • When KES keys are rotated, update KES_SECRET_KEY_PATH and OPERATIONAL_CERTIFICATE_PATH in the environment file if needed, then restart the service
note

For the complete step-by-step instructions, including build commands, environment file examples, and service configuration, see Set up the Mithril signer node in the Mithril documentation.

Resources​