Open HRMP channel between KICO and Karura

TL;DR

Similar with the earlier Kintsugi proposal , we propose to open HRMP communication between KICO and Karura.

Summary

We propose to open a bi-directional channel between Kurara and KICO. Initially, the main usecase will be to transfer KICO and kUSD between the two chains, KICO introduces kUSD for liquidity mining and stable currency use.

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 KICO HRMP channel
  2. Wait until proposal on step 1 get approved & encated
  3. KICO propose to accept the request and request to open KICO to Karura HRMP channel(Batch call)
  4. Wait until proposal on step 3 get approved & encated
  5. Karura propose to accept KICO 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: 2107, proposedMaxCapacity: 1000, proposedMaxMessageSize: 102400) , which hex-encoded is 0x3c003b080000e803000000900100
  • 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 0x1800083c01d00700003c00d0070000e803000000900100
  • For step 5: hrmp.hrmpAcceptOpenChannel(sender: 2107) , which hex-encoded is 0x3c013b080000

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 KICO 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 a open request call and a accept request call with its orml-xcm pallet.

xcmPallet.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: 0x1800083c01d00700003c00d0070000e803000000900100
          }
        }
       }
       {
         RefundSurplus
       }
       {
          DepositAsset: {
           assets: {
             Wild: All
           }
           maxAssets: 1
           beneficiary: {
             parents: 0
             interior: {
                X1: {
                 AccountId32: {
                  network: Any
                  id: 
  <account-to-receive-leftover-assets>
                 }
               }
             }
          }
        }
      }
    ]
  }
 )

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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