# Validator Security

Learn about sentry nodes and HSMs to secure a validator

Each validator candidate is encouraged to run its operations independently, as diverse setups increase the resilience of the network. Validator candidates should commence their setup phase now in order to be on time for launch.

# Horcrux

Horcrux is a multi-party-computation (MPC) (opens new window) signing service for Tendermint nodes

Take your validator infrastructure to the next level of security and availability:

• Composed of a cluster of signer nodes in place of the remote signer (opens new window), enabling High Availability (HA) for block signing through fault tolerance.
• Secure your validator private key by splitting it across multiple private signer nodes using threshold Ed25519 signatures
• Add security and availability without sacrificing block sign performance.

See documentation here (opens new window) to learn how to upgrade your validator infrastructure with Horcrux.

# Tendermint KMS

Tendermint KMS is a signature service with support for Hardware Security Modules (HSMs), such as YubiHSM2 and Ledger Nano . It’s intended to be run alongside Cosmos Validators, ideally on separate physical hosts, providing defense-in-depth for online validator signing keys, double signing protection, and functioning as a central signing service that can be used when operating multiple validators in several Cosmos Zones.

For more details, please see Tendermint KMS

# Hardware HSM

It is mission critical that an attacker cannot steal a validator's key. If this is possible, it puts the entire stake delegated to the compromised validator at risk. Hardware security modules are an important strategy for mitigating this risk.

HSM modules must support ed25519 signatures for Haqq. The YubiHSM 2 (opens new window) supports ed25519 and can be used with this YubiKey library (opens new window).

🚨 IMPORTANT: The YubiHSM can protect a private key but cannot ensure in a secure setting that it won't sign the same block twice.

# Sentry Nodes (DDOS Protection)

Validators are responsible for ensuring that the network can sustain denial of service attacks.

One recommended way to mitigate these risks is for validators to carefully structure their network topology in a so-called sentry node architecture.

Validator nodes should only connect to full-nodes they trust because they operate them themselves or are run by other validators they know socially. A validator node will typically run in a data center. Most data centers provide direct links the networks of major cloud providers. The validator can use those links to connect to sentry nodes in the cloud. This shifts the burden of denial-of-service from the validator's node directly to its sentry nodes, and may require new sentry nodes be spun up or activated to mitigate attacks on existing ones.

Sentry nodes can be quickly spun up or change their IP addresses. Because the links to the sentry nodes are in private IP space, an internet based attacked cannot disturb them directly. This will ensure validator block proposals and votes always make it to the rest of the network.

To setup your sentry node architecture you can follow the instructions below:

Validators nodes should edit their config.toml:

Copy # Comma separated list of nodes to keep persistent connections to # Do not add private peers to this list if you don't want them advertised persistent_peers =[list of sentry nodes] # Set true to enable the peer-exchange reactor pex = false

Sentry Nodes should edit their config.toml:

Copy # Comma separated list of peer IDs to keep private (will not be gossiped to other peers) # Example ID: 3e16af0cead27979e1fc3dac57d03df3c7a77acc@3.87.179.235:26656 private_peer_ids = "node_ids_of_private_peers"

# Environment Variables

By default, uppercase environment variables with the following prefixes will replace lowercase command-line flags:

• EVMOS (for Haqq flags)
• TM (for Tendermint flags)
• BC (for democli or basecli flags)

For example, the environment variable HAQQ_CHAIN_ID will map to the command line flag --chain-id. Note that while explicit command-line flags will take precedence over environment variables, environment variables will take precedence over any of your configuration files. For this reason, it's imperative that you lock down your environment such that any critical parameters are defined as flags on the binary or prevent modification of any environment variables.