PoA Module

The Proof of Authority (PoA) module allows for permissioned networks to be controlled by a predefined set of validators to verify transactions. This implementation extends the Cosmos-SDK's x/staking module to a a set of administrators over the chain. These administrators gate keep the chain by whitelisting validators, updating cosnensus power, and removing validators from the network.

Integration

Since this module depends on x/staking, carefully read through the Integration Guide to add it to your network. This design choice was made to allow for the PoA module to have backwards compatibility with:

• Website UIs
• Uptime bots
• Validator scripts
• in-process multi-validator testnets

Configuration

After integrating the PoA module into your chain, read the network considerations before launching the network.

This includes: parameters, full module control, migrating from PoA->PoS, and other useful information.

Concepts

The PoA flow is divided into a few key steps:

• GenTx: Validators submit standard genesis transactions with the app binary CLI wrapper
• Start: The chain controller merges these genesis transactions into the genesis file and starts the chain
• Updates: The chain admin(s) can update the validator set by adding validators or modifying their consensus power.
• Removal: The chain admin(s) can remove validators from the network.

All delegation actions are disabled with the disabled-staking ante. While the validator is the set delegator of its own account, only the admin(s) can modify this delegation of power via x/poa. Validators can only go down the following ways:

Module	Action
x/slashing	downtime
x/slashing	double sign
x/poa	admin removal
x/poa	self removal

State

Genesis

Params is found in the genesis state. This object contains the admins field, which is a list of bech32 addresses that are allowed to modify the validator set, PoA params, and validator params (via x/staking). If no admin is set, then the chain should set the governance account as the admin (default). By allowing for an array of admins, the chain can be controlled by multiple different parties according to your use case. For example, governance can be an admin while also allowing a multisig, DAO, and/or single account to control the validator set. There must be at least one admin in the list at all times.

AllowValidatorSelfExit is a boolean option (default true) that toggles validators ability to remove themselves from the active set. This is useful for validators that are no longer able or decide this PoA network is no longer for them. If set to false, only admins can remove validators from the set. NOTE This does not stop validators from going down and being jailed for downtime. It just provides a graceful way to self remove power.

Pending Validators

PendingValidators stores an array of PoA validator objects pending approval (from the admins) into the active set. This only is required after the chain has started.

For better UX, this is accomplished by wrapping the x/staking module's create-validator command with our own logic. Validators only have to modify the namespace of their create command (from tx staking create-validator -> tx poa create-validator) with all else being equal.

Previous Block Power

CachedPreviousBlockPower saves the previous blocks total consensus power amount for queries at Height + 1. It allows for safety checks onm updating too much of the sets power resulting in broken IBC connections. It's protection can be passed by using the --unsafe flag in the set-power CLI command.

Absolute Changed Block Power

AbsoluteChangedInBlockPower tracks the per block modification in block power. It follows the absolute power difference a single block can change against the previous block power. Attempting to increase more than 30% of the validator set power (relative to last) will error.

Flow:

• Validator previous block set power is 9 (3 validators @ 3 power)
• The admin increases validator[0] to 4 power (+11%)
• The admin increases validator[1] to 4 power (+22%)
• The admin increases validator[2] to 4 power (+33%, error)

The AbsoluteChangedPower of +1 to each validator is 3, which is 33% of the previous block power (3/9). It can be bypassed with the use of the --unsafe flag in the CLI command.

Messages

CreateValidator

{
  "@type": "/strangelove_ventures.poa.v1.MsgCreateValidator",
  "description": {
    "moniker": "Validator Name",
    "identity": "",
    "website": "https://website.com",
    "security_contact": "[email protected]",
    "details": "description"
  },
  "commission": {
    "rate": "0.100000000000000000",
    "max_rate": "0.200000000000000000",
    "max_change_rate": "0.010000000000000000"
  },
  "min_self_delegation": "1",
  "delegator_address": "",
  "validator_address": "cosmosvaloper1addr",
  "pubkey": {
    "@type": "/cosmos.crypto.ed25519.PubKey",
    "key": "pl3Q8OQwtC7G2dSqRqsUrO5VZul7l40I+MKUcejqRsg="
  }
}

SetPower (admin only)

• power is a micro unit of power (1,000,000 = 1 power) to derive a validators consensus power.
• unsafe allows an admin to bypass the 30% of consensus power per block limitation.

{
  "@type": "/strangelove_ventures.poa.v1.MsgSetPower",
  "sender": "cosmos1addr",
  "validator_address": "cosmosvaloper1addr",
  "power": "12356789",
  "unsafe": true
}

RemoveValidator (admin only)

{
  "@type": "/strangelove_ventures.poa.v1.MsgRemoveValidator",
  "sender": "cosmos1addr",
  "validator_address": "cosmosvaloper1addr"
}

RemovePending (admin only)

{
  "@type": "/strangelove_ventures.poa.v1.MsgRemovePending",
  "sender": "cosmos1hj5fveer5cjtn4wd6wstzugjfdxzl0xpxvjjvr",
  "validator_address": "cosmosvaloper1efd63aw40lxf3n4mhf7dzhjkr453axurlv4rfe"
}

UpdateParams (admin only)

• admins is a list of bech32 addresses that control the validator set and parameters of the chain.
• allow_validator_self_exit allows validators to force remove themselves from the active set at any time.

{
  "@type": "/strangelove_ventures.poa.v1.MsgUpdateParams",
  "sender": "cosmos1addr",
  "params": {
    "admins": [
      "cosmos1addr",
      "cosmos1addr1",
      "cosmos1addr2",
    ],
    "allow_validator_self_exit": true
  }
}

UpdateStakingParams (admin only)

{
  "@type": "/strangelove_ventures.poa.v1.MsgUpdateStakingParams",
  "sender": "cosmos1hj5fveer5cjtn4wd6wstzugjfdxzl0xpxvjjvr",
  "params": {
    "unbonding_time": "1209600s",
    "max_validators": 100,
    "max_entries": 7,
    "historical_entries": 7,
    "bond_denom": "stake",
    "min_commission_rate": "0.000000000000000000"
  }
}

Begin Block

As the PoA logic is dependent on the x/staking module, the PoA module must be run before the x/staking modules BeginBlock logic. This is described in the integration guide.

When removing validators, the validator can not be instantly removed from the set and it required a few intermediate blocks.

Flow

A validator is removed by an admin at height H; it increases the minimum self delegation to current+1. This puts the bonded validator into Unbonding status when checked by the x/staking module in it's BeginBlock (at H). The next iteration (H+1) the PoA module force updates the Unbonding validator to the status of Unbonded. The x/staking module then performs it's BeginBlock logic and sets it as Unbonded. The validator is now deleted from consensus at H+2 in the PoA BeginBlock.

Client

LCD / API	gRPC
/poa/v1/params	strangelove_ventures.poa.v1.Query/Params
/poa/v1/pending_validators	strangelove_ventures.poa.v1.Query/PendingValidators
/poa/v1/{consensus_power}	strangelove_ventures.poa.v1.Query/ConsensusPower

CLI

A user can query and interact with the poa module using the CLI.

Query

The query commands allow users to query the poa state.

# Get module params (admins list)
poad q poa params

# Get validators waiting to be added to the set
poad q poa pending-validators

# Get the current consensus power of a specific validator
poad q poa power [validator]

To get validator specific information such as commission rates, details, etc. use the x/staking module's query commands.

# e.g. validator, validators, params
poad q staking --help

Transactions

The tx commands allow users to interact and update the poa state.

# Create a validator and add it to the pending set
poad tx poa create-validator path/to/validator.json --from keyname

# (admin) Remove a validator from the set and delete them
poad tx poa remove [validator]

# (admin) Modify the consensus power of a validator
# - validator is the bech32 address of the validator operator
# - amount uses 10^6 precision (1,000,000 = 1 power)
# - --unsafe flag allows for bypassing the 30% max change per block
poad tx poa set-power [validator] [amount] [--unsafe]

# (admin) Update the PoA module params
# - admins is a comma separated list of bech32 addresses
# - any admin can modify the list at any time
# - there must be at least one admin in the list at all times
# - allow_validator_self_exit is a bool to allow validators to force remove themselves from the set.
poad tx poa update-params [admin1,admin2,admin3,...] [allow_validator_self_exit]

# (admin) Update the staking module params
# - unbondingTime is the time that a validator must wait to unbond (ex: 336h)
# - maxVals is the maximum number of validators for the active set.
# - maxEntries is the maximum number of unbonding delegations per validator (does not apply for PoA)
# - historicalEntries is the maximum number of historical entries stored per validator (does not apply for PoA)
# - bondDenom is the denom of the bond token (e.g. uatom)
# - minCommissionRate is the minimum commission rate a validator can set
poad tx poa update-staking-params [unbondingTime] [maxVals] [maxEntries] [historicalEntries] [bondDenom] [minCommissionRate]

Appendix

• Cosmos-SDK Staking Module