0009_guardian_key.md

Guardian Key Usage

Objective

• Describe how guardian keys are used and how message confusion is avoided.

Background

Message confusion could occur when a Guardian signs a message and an attacker replays that message elsewhere where it is interpreted as a different message type, which could lead to unintended behavior.

Overview

The Guardian Key is used to:

1. Sign gossip messages
   1. heartbeat
   2. governor config and governor status
   3. observation request
2. Sign Observations
   1. Version 1 VAAs
3. Sign Guardian identification
   1. Wormchain account registration
4. Sign Accountant observations
   1. Token Bridge
   2. NTT
5. Sign Query responses

Detailed Design

Signing of gossip messages:

1. Prepend the message type prefix to the payload
2. Compute Keccak256Hash of the payload.
3. Compute ethcrypto.Sign()

Signing of Observations:

• v1 VAA: double-Keccak256(observation).

Rationale

• Gossip messages cannot be confused with other gossip messages because the message type prefix is prepended.
• Gossip messages cannot be confused with observations because observations utilize a double-Keccak256 and the payload is enforced to be >=34 bytes.

Prefixes Used

acct_sub_obsfig_000000000000000000| // token bridge accountant observation
ntt_acct_sub_obsfig_00000000000000| // ntt accountant observation
governor_config_000000000000000000| // gossip governor config
governor_status_000000000000000000| // gossip governor status
heartbeat|                          // gossip heartbeat
signed_observation_request|         // gossip signed observation request
mainnet_query_request_000000000000| // query request (mainnet, not signed by guardian)
testnet_query_request_000000000000| // query request (testnet, not signed by guardian)
devnet_query_request_0000000000000| // query request (devnet, not signed by guardian)
query_response_0000000000000000000| // query response
query_response_0000000000000000000| // query response
signed_wormchain_address_00000000|  // wormchain register account as guardian