Open HRMP channel between Crust Shadow and Karura

TL;DR

Similar with the earlier Khala proposal , we propose to open HRMP communication between Crust Shadow and Karura.

Summary

We propose to open a bi-directional channel between Kurara and Crust Shadow. Initially, the main use-case will be to transfer CSM between the two chains, as a necessary step for the pre-proposal for list $CSM on Karura pools

Proposal

There is no on-chain proposal yet; #TBD.

Technical details:

The procedure for opening the channels is as follows:

  1. Karura propose to request to open Karura to Crust Shadow HRMP channel
  2. Wait until the proposal on step 1 get approved & enacted
  3. Crust Shadow propose to accept the request and request to open Crust Shadow to Karura HRMP channel(Batch call)
  4. Wait until the proposal on step 3 get approved & enacted
  5. Karura propose to accept Crust Shadow to Karura HRMP channel
  6. Wait until proposals on step 5 are approved & enacted
  7. Wait for another session on Kusama for the change to be effective
  8. XCM based cross-chain transfer will be possible at this stage.

The extrinsics that need to be executed on the relay chain , are:

  • For step 1: hrmp.hrmpInitOpenChannel(recipient: 2012, proposedMaxCapacity: 1000, proposedMaxMessageSize: 102400) , which hex-encoded is 0x3c00dc070000e803000000900100
  • For step 3: first call is hrmp.hrmpAcceptOpenChannel(sender: 2000) , second call is hrmp.hrmpInitOpenChannel(recipient: 2000, proposedMaxCapacity: 1000, proposedMaxMessageSize: 102400) , the batch call hex-encoded is 0x1802083c01d00700003c00d0070000e803000000900100
  • For step 5: hrmp.hrmpAcceptOpenChannel(sender: 2012) , which hex-encoded is 0x3c01dc070000

The proposedMaxCapacity and proposedMaxMessageSize are set to the values of Kusama’s configuration.activeConfig.hrmpChannelMaxCapacity and configuration.activeConfig.hrmpChannelMaxMessageSize values, respectively.

These extrinsics need to be called with the parachain’s sovereign account as origin. To achieve this, on the Crust Shadow side we will use polkadot-xcm pallet to send xcm message to the relaychain, by executing the following extrinsic from the parachain. Karura should make an open request call and an accept request call with its orml-xcm pallet.

polkadotXcm.send(
  dest: XcmVersionedMultiLocation
  {
    V1: {
      parents: 1
      interior: Here
    }
  }
  
  message: XcmVersionedXcm
  {
    V2: [
      {
        WithdrawAsset: [
          {
            id: {
              Concrete: {
                parents: 0
                interior: Here
              }
            }
            fun: {
              Fungible: 100,000,000,000
            }
          }
        ]
      }
      {
        BuyExecution: {
          fees: {
            id: {
              Concrete: {
                parents: 0
                interior: Here
              }
            }
            fun: {
              Fungible: 100,000,000,000
            }
          }
          weightLimit: Unlimited
        }
      }
      {
        Transact: {
          originType: Native
          requireWeightAtMost: 1,000,000,000
          call: {
            encoded: 0x1802083c01d00700003c00d0070000e803000000900100
          }
        }
      }
      {
        RefundSurplus
      }
      {
        DepositAsset: {
          assets: {
            Wild: All
          }
          maxAssets: 1
          beneficiary: {
            parents: 0
            interior: {
              X1: {
                AccountId32: {
                  network: Any
                  id: 0x70617261dc070000000000000000000000000000000000000000000000000000
                }
              }
            }
          }
        }
      }
    ]
  }
)

As a prerequisite, the parachain’s sovereign account must contain at least 10 KSM to be locked as collateral (5 for each channel direction), plus some KSM to pay for xcm execution fees.

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