Tendermint KMS + Ledger

Set up Tendermint KMS with the Tendermint Ledger app {synopsis}

Pre-requisites

Checklist

::: warning šŸš§ The following instructions are a brief walkthrough and not a comprehensive guideline. You should consider and research more about the security implications of activating an external KMS. :::

  • āœ… Ledger Nano X or Nano S device (compare here)
  • āœ… Ledger Live installed
  • āœ… Tendermint app installed (only in Developer Mode)
  • āœ… Latest Versions (Firmware and Tendermint app)

Tendermint Validator app (for Ledger devices)

::: danger šŸšØIMPORTANT: KMS and Ledger Tendermint app are currently work in progress. Details may vary. Use under your own risk :::

You should be able to find the Tendermint app in Ledger Live.

::: tip You will need to enable Developer Mode in Ledger Live Settings in order to find the app. :::

KMS configuration

In this section, we will configure a KMS to use a Ledger device running the Tendermint Validator App.

Config file

You can find other configuration examples here

  • Create a ~/.tmkms/tmkms.toml file with the following content (use an adequate chain_id)

    # Example KMS configuration file
    [[validator]]
    addr = "tcp://localhost:26658"                  # or "unix:///path/to/socket"
    chain_id = "kynno_9701-1"
    reconnect = true                                # true is the default
    secret_key = "~/.tmkms/secret_connection.key"
    
    [[providers.ledger]]
    chain_ids = ["kynno_9701-1"]
    
  • Edit addr to point to your kynnod instance.

  • Adjust chain-id to match your .kynnod/config/config.toml settings.

  • provider.ledger has not additional parameters at the moment, however, it is important that you keep that header to enable the feature.

Plug your Ledger device and open the Tendermint validator app.

Generate secret key

Now you need to generate a secret_key:

tmkms keygen ~/.tmkms/secret_connection.key

Retrieve validator key

The last step is to retrieve the validator key that you will use in kynnod.

Start the KMS:

tmkms start -c ~/.tmkms/tmkms.toml

The output should look similar to:

07:28:24 [INFO] tmkms 0.11.0 starting up...
07:28:24 [INFO] [keyring:ledger:ledger] added validator key kynnovalconspub1zcjduepqy53m39prgp9dz3nz96kaav3el5e0th8ltwcf8cpavqdvpxgr5slsd6wz6f
07:28:24 [INFO] KMS node ID: 1BC12314E2E1C29015B66017A397F170C6ECDE4A

The KMS may complain that it cannot connect to kynnod. That is fine, we will fix it in the next section. This output indicates the validator key linked to this particular device is: kynnovalconspub1zcjduepqy53m39prgp9dz3nz96kaav3el5e0th8ltwcf8cpavqdvpxgr5slsd6wz6f Take note of the validator pubkey that appears in your screen. We will use it in the next section.

Kynno configuration

You need to enable KMS access by editing .kynnod/config/config.toml. In this file, modify priv_validator_laddr to create a listening address/port or a unix socket in kynnod.

For example:

...
# TCP or UNIX socket address for Tendermint to listen on for
# connections from an external PrivValidator process
priv_validator_laddr = "tcp://127.0.0.1:26658"
...

Let's assume that you have set up your validator account and called it kmsval. You can tell kynnod the key that we've got in the previous section.

kynnod gentx --name kmsval --pubkey <pub_key>

Now start kynnod. You should see that the KMS connects and receives a signature request.

Once the Ledger device receives the first message, it will ask for confirmation that the values are adequate.

Tendermint Ledger app "Init Validation"

Click the right button, if the height and round are correct.

After that, you will see that the KMS will start forwarding all signature requests to the Ledger app:

Tendermint Ledger app "Proposal"

::: warning The word TEST in the second picture, second line appears because they were taken on a pre-release version. Once the app as been released in Ledger's app store, this word should NOT appear. :::