Polkadot <> Kusama Bridge

Ecosystem
18

Updates

P<>K Bridge

  • Polkadot AssetHub spec_version: 1001002 and Polkadot BridgeHub spec_version: 1001000 containing bridging capabilities has been enacted on-chain today :bridge_at_night: .
  • Kusama AssetHub spec_version: 1001002 and Kusama BridgeHub spec_version: 1001000 containing bridging capabilities had been enacted on-chain since a couple of weeks :bridge_at_night: .
  • The two above combined means we can launch the bridge :rocket: .
  • Starting to prepare governance motions to configure and enable the bridge :judge:.

BEEFY

  • Kusama: BEEFY consensus :cut_of_meat: started today on Kusama, now live :tada: .
  • Polkadot spec_version: 1001002 containing BEEFY capabilities enacted on chain.
  • Polkadot Validators :construction_worker_man: need to rotate their keys to register their BEEFY :cut_of_meat: keys.
    • once we reach healthy percentage of validators with valid BEEFY keys, we can enable on Polkadot too.

FAQs

Answering some FAQs here:

only KSM & DOT supported initially - how are additional assets added? What is the time frame for such additions? would be excellent to get USDT (Polkadot AH) on Kusama ASAP

Other assets can be easily (but has to go through governance) added and they will be added on a per-request basis after the bridge launch - USDT to Kusama is high on our list and will be among the first to be added.

the cost to send XCMs across bridge is 2.4 DOT or 0.4 KSM (depending on direction) - that seems rather high, is there a TLDR as to why its much higher than e.g. standard XCM and if there’s scope for that being lowered long term?

There is a cost analysis available here.

The high cost is coming from the trustless property of the bridge - all the proofs required to be submitted on-chain are pretty big and thus pretty costly.
The cost of a single XCM sent across has some “bridge transport base” + XCM costs, where the bridge base is a big chunk (all the state/consensus proofs required) which is also rather fixed - so a simple XCM costs approximately the same as a complex/big XCM.
So one of the first workarounds available to users since Day 1 is to try to batch multiple operations in single XCM, thus lowering per-operation cost.

There is definitely scope to lower costs long term, but no work is scheduled/budgeted on this topic yet.
We’re looking to You - the Polkadot community - to decide where to focus our resources. Improvements in this area come with non-negligible development cost, so we first want to see how much of a pain point the current (high) fees really are, and make a data-driven cost-benefit analysis.

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