Open HRMP channel between Parallel Heiko and Karura

TL;DR

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

Summary

We propose to open a bi-directional channel between Kurara and Parallel Heiko. Initially, the main usecase will be to transfer HKO and KAR between the two chains and bring some Karura assets to the coming Parallel products such as Money Market, AMM and pMaker.

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 Parallel Heiko HRMP channel
  2. Wait until proposal on step 1 get approved & encated
  3. Parallel Heiko propose to accept the request and request to open Parallel Heiko to Karura HRMP channel(Batch call)
  4. Wait until proposal on step 3 get approved & encated
  5. Karura propose to accept Parallel Heiko 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 crosschain 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: 2085, proposedMaxCapacity: 1000, proposedMaxMessageSize: 102400) , which hex-encoded is 0x3c0025080000e803000000900100
  • 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: 2085) , which hex-encoded is 0x3c0125080000

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 Parallel Heiko side we will use orml-xcm pallet to send xcm message to the relaychain, by executing the following extrinsic from the parachain. Karura should make a open request call and a accept request call with its orml-xcm pallet.

ormlXcm.send(
  dest: XcmVersionedMultiLocation
  {
    V1: {
      parents: 1
      interior: Here
    }
  },
  message: XcmVersionedXcm
  {
    V2: [
      {
        WithdrawAsset: [
          {
            id: {
              Concrete: {
                parents: 0,
                interior: 'Here'
              }
            },
            fun: {
              Fungible: '1000000000000'
            }
          }
        ]
      },
      {
        BuyExecution: {
          fees: {
            id: {
              Concrete: {
                parents: 0,
                interior: 'Here'
              }
            },
            fun: {
              Fungible: '1000000000000'
            }
          },
          weightLimit: 'Unlimited'
        }
      },
      {
        Transact: {
          originType: 'Native',
          requireWeightAtMost: '1000000000',
          call: {
            encoded: 0x1802083c01d00700003c00d0070000e803000000900100
          }
        }
      },
      {
        DepositAsset: {
          assets: {
            Wild: 'All'
          },
          maxAssets: 1,
          beneficiary: {
            parents: 0,
            interior: {
              X1: {
                AccountId32: {
                  network: 'Any',
                  id: 0x7061726125080000000000000000000000000000000000000000000000000000
                }
              }
            }
          }
        }
      }
    ]
  }
})

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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