9f143a9742
The Processor's coins folder referred to the networks it could process, as did its Coin trait. This, and other similar cases throughout the codebase, have now been corrected. Also corrects dated documentation for a key pair is confirmed under the validator-sets pallet.
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Validator Sets
Validator Sets are defined at the protocol level, with the following parameters:
bond(Amount): Amount of bond per key-share.network(Network): The network this validator set operates over.participants(Vec<SeraiAddress>): List of participants within this set.
Validator Sets are referred to by NetworkId yet have their data accessible via
ValidatorSetInstance.
Participation in consensus
All Validator Sets participate in consensus. In the future, a dedicated group to order Serai is planned.
Multisig
Every Validator Set is expected to form a t-of-n multisig, where n is the
amount of key shares in the Validator Set and t is n * 2 / 3 + 1, for each
of its networks. This multisig is secure to hold coins up to 67% of the
Validator Set's bonded value. If the coins exceed that threshold, there's more
value in the multisig than in the supermajority of bond that must be put forth
to control it. Accordingly, it'd be no longer financially secure, and it MUST
reject newly added coins which would cross that threshold.
Multisig Creation
Multisigs are created by processors, communicating via their Coordinators.
They're then confirmed on chain via the validator-sets pallet. This is done by
having 100% of participants agree on the resulting group key. While this isn't
fault tolerant regarding liveliness, a malicious actor who forces a t-of-n
multisig to be t-of-n-1 reduces the fault tolerance of the created multisig
which is a greater issue. If a node does prevent multisig creation, other
validators should issue slashes for it/remove it from the Validator Set
entirely.
Placing the creation on chain also solves the question of if the multisig was successfully created or not. Processors cannot simply ask each other if they succeeded without creating an instance of the Byzantine Generals Problem. Placing results within a Byzantine Fault Tolerant system resolves this.
Multisig Lifetime
The keys for a Validator Set remain valid until its participants change. If a Validator Set adds a new member, and then they leave, the set's historical keys are not reused.
Multisig Handoffs
Once new keys are confirmed for a given Validator Set, they become tracked and the recommended set of keys for incoming coins. The old keys are still eligible to receive coins for a provided grace period, requiring the current Validator Set to track both sets of keys. The old keys are also prioritized for handling outbound transfers, until the end of the grace period, at which point they're no longer eligible to receive coins and they forward all of their coins to the new set of keys. It is only then that validators in the previous instance of the set, yet not the current instance, may unbond their stake.
Set Keys (message)
network(Network): Network whose key is being voted for.key_pair(KeyPair): Key pair being set for thisSession.signature(Signature): A MuSig-style signature of all validators, confirming this key.
Once a key is voted on by every member, it's adopted as detailed above.