Partial Set Security

The Partial Set Security (PSS) feature allows consumer chains to join as Opt-In or Top N. Here, we show how a validator can opt in, opt out, or set a custom commission rate on a consumer chain, as well as useful queries that a validator can use to figure out which chains it has to validate, etc.

Messages

How to opt in to a consumer chain?

warning

A validator is automatically opted in to a Top N chain if the validator belongs to the top N% of the validators on the provider chain.

In a Top N chain, a validator that does not belong to the top N% of the validators on the provider can still choose to opt in to a consumer chain. In other words, validators can opt in, in both Opt-In and Top N chains.

A validator can opt in to a consumer chain by issuing the following message:

interchain-security-pd tx provider opt-in <consumer-id> <optional consumer-pub-key>

where

• consumer-id is the consumer id identifier of the consumer chain the validator wants to opt in to;
• consumer-pub-key corresponds to the public key the validator wants to use on the consumer chain, and it has the following format {"@type":"/cosmos.crypto.ed25519.PubKey","key":"<key>"}.

A validator can opt in to any active consumer chain, so a validator can opt in to a chain even before it launches. A validator can use the following command to retrieve the currently existing consumer chains:

interchain-security-pd query provider list-consumer-chains

By setting the consumer-pub-key, a validator can both opt in to a chain and assign a public key on a consumer chain. Note that a validator can always assign a new consumer key at a later stage. The key-assignment rules still apply when setting consumer-pub-key when opting in.

warning

Validators are strongly recommended to assign a separate key for each consumer chain and not reuse the provider key across consumer chains for security reasons.

Note that a validator is only eligible for consumer rewards from a consumer chain if the validator is opted into that chain.

How to opt out from a consumer chain?

A validator can opt out from a consumer by issuing the following message:

interchain-security-pd tx provider opt-out <consumer-chain-id>

where

• consumer-id is the consumer identifier of the consumer chain.

The opting out mechanism has the following rules:

• A validator cannot opt out from a Top N chain if it belongs to the top N% validators of the provider.
• If a validator moves from the Top N to outside of the top N% of the validators on the provider, it will not be automatically opted-out. The validator has to manually opt out.
• A validator should stop its node on a consumer chain only after opting out and confirming through the has-to-validate query (see below) that it does not have to validate the consumer chain any longer. Otherwise, the validator risks getting jailed for downtime.

warning

If all validators opt out from an Opt-In chain, the chain will halt with a consensus failure upon receiving the VSCPacket with an empty validator set.

How to set specific per consumer chain commission rate?

A validator can choose to set a different commission rate on each of the consumer chains. This can be done with the following command:

interchain-security-pd tx provider set-consumer-commission-rate <consumer-id> <commission-rate>

where

• consumer-id is the consumer identifier of the consumer chain;
• comission-rate decimal in [minRate, 1] where minRate corresponds to the minimum commission rate set on the provider chain (see min_commission_rate in interchain-security-pd query staking params).

If a validator does not set a commission rate on a consumer chain, the commission rate defaults to their commission rate on the provider chain.

Validators can set their commission rate even for consumer chains that they are not currently opted in on, and the commission rate will be applied when they opt in. This is particularly useful for Top N chains, where validators might be opted in automatically, so validators can set the commission rate in advance.

If a validator opts out and then back in, this will not reset their commission rate back to the default. Instead, their set commission rate still applies.

Queries

PSS introduces a number of queries to assist validators in determining which consumer chains they have to validate, their commission rate per chain, etc.

Which chains does a validator have to validate?

Naturally, a validator is aware of the Opt-In chains it has to validate because in order to validate an Opt-In chain, a validator has to manually opt in to the chain. This is not the case for Top N chains where a validator might be required to validate such a chain without explicitly opting in if it belongs to the top N% of the validators on the provider.

We introduce the following query:

interchain-security-pd query provider has-to-validate <provider-validator-address>

that can be used by validator with provider-validator-address address to retrieve the list of chains that it has to validate.

warning

For a validator, the list of chains returned by has-to-validate is the list of chains the validator should be validating to avoid getting jailed for downtime.

How do you know how much voting power you need to have to be in the top N for a chain?

This can be seen as part of the list-consumer-chains query:

interchain-security-pd query provider list-consumer-chains

where the min_power_in_top_N field shows the minimum voting power required to be automatically opted in to the chain.

Note that list-consumer-chains shows the minimal voting power right now, but the automatic opt-in happens only when epochs end on the provider. In consequence, a validators power might be large enough to be automatically opted in during an epoch, but if their power is sufficiently decreased before the epoch ends, they will not be opted in automatically.

How to retrieve all the opted-in validators on a consumer chain?

With the following query:

interchain-security-pd query provider consumer-opted-in-validators <consumer-id>

we can see all the opted-in validators on consumer-id that were manually or automatically opted in.

How to retrieve all the consumer validators on a consumer chain?

With the following query:

interchain-security-pd query provider consumer-validators <consumer-id>

we can see all the consumer validators (i.e., validator set) of consumer-id. The consumer validators are the ones that are currently (or in the future, see warning) validating the consumer chain. A consumer validator is an opted-in validator but not vice versa. For example, an opted-in validator V might not be a consumer validator because V is denylisted or because V is removed due to a validator-set cap.

Note that the returned consumer validators from this query do not necessarily correspond to the validator set that is validating the consumer chain at this exact moment. This is because the VSCPacket sent to a consumer chain might be delayed and hence this query might return the validator set that the consumer chain would have at some future point in time.

How can we see the commission rate a validator has set on a consumer chain?

Using the following query:

interchain-security-pd query provider validator-consumer-commission-rate <consumer-id> <provider-validator-address>

we retrieve the commission rate set by validator with provider-validator-address address on consumer-id.