Greycore

The Greycore is a special community governed shard that backs all gateway shards and the coordination shard. The Greycore has two core purposes:

1. guaranteeing the safety of assets under management by acting as a second signature on all minting and releasing (see Gateways), and
2. guaranteeing the uniform randomness of shard selection by generating secure random numbers (see Sharding).

In RenVM SubZero, members of the Greycore will be selected by the Ren team. By RenVM One, members will be selected through community governance. It is recommended that community members select members that have stake in the success of RenVM; projects/protocols that use RenVM for interoperability are incentivised by the success of their own ecosystems to resist bribery attempts, and investors backing these projects/protocols are also similarly incentivised. Community governance over membership ensures that the Greycore remains decentralised.

Safety

The addition of a second signature requirement on all minting and releasing transactions improves safety. This is because an adversary must still attack gateway shards as if there was no Greycore, and then also attack the Greycore itself. Similarly, the coordination shard becomes more difficult to attack.

Liveliness

The addition of a second signature requirement on all minting and releasing, if implemented naïvely, reduces liveliness. This is because an adversary can now choose to attack the Greycore instead of the normal gateway/coordination shards.

However, this can be mitigated by making sustained liveliness attacks on the Greycore harder than liveliness attacks in the gateway/coordination shards. This is achieved through the governance mechanism that selects members; if members of the Greycore become unresponsive, then they can be removed by the governance mechanism. This constant pruning of inactive Greycore members means that up to 2/3rd- of the Greycore can go offline simultaneously and liveliness can still be recovered.

References

• Gateways
• Sharding