[Referendum: 119] Open/Accept HRMP channel to/from Robonomics and Register XRT Asset


This batched proposal is to Accept/Open an HRMP channel with Robonomics and to register the XRT token


We propose to open a bi-directional channel between Moonriver and Robonomics. Initially, the main use case will be to transfer XRT between the two chains, but it can be further expanded to other use cases. The proposal also includes the XRT asset registration as xcXRT, with the following details:

  • Multilocation: { “parents”: 1, “interior”: {“X1”: { “Parachain”: 2048}}}
  • Decimals: 9
  • Name: XRT
  • Symbol: xcXRT

xcXRT will have the following asset ID and XC-20 address:

  • Asset ID: 108036400430056508975016746969135344601
  • XC-20 address: 0xffffffff51470dca3dbe535bd2880a9ccdbc6bd9


Proposal #31 with the following hash: 0x6d75c250e5ce6e0b87cd7c42dad117783bd2f0ccd648d90e5180051b40e448d6

Technical details:

The procedure for opening the channels is as follows:

  • Robonomics: already proposed to open an HRMP channel to Moonriver
  • Moonriver: democracy batched proposal:
    • Open Moonriver to Robonomics HRMP channel
    • Accept Robonomicsto Moonriver HRMP channel
    • Register XRT asset as an XC-20
  • Robonomics: democracy proposal to accept Moonriver to Robonomics HRMP channel

Once the HRMP channels are ready, XCM based cross-chain transfer will be possible. The extrinsics that need to be executed on the relay chain, are:

  • To accept the HRMP channel to Moonriver: hrmp.hrmpAcceptOpenChannel(sender: 2048) , which hex-encoded call data is 0x3c0100080000
  • To open the HRMP channel from Moonriver: hrmp.hrmpInitOpenChannel(recipient: 2048, proposedMaxCapacity: 1000, proposedMaxMessageSize: 102400), which its hex-encoded call data is 0x3c0000080000e803000000900100

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

These extrinsics need to be called from the parachain’s sovereign account as origin, via a democracy proposal. The proposal will use polkadotXcm pallet to send XCM message to the Relay Chain with the following items:

  • Withdraw asset: take funds out of the Sovereign Account of the origin parachain (in the relay chain) to a holding state
  • Buy execution: buys execution time from the relay chain, to execute the XCM message
  • Transact: provides the call data to be executed
  • Deposit asset (optional): refunds the leftover funds after the execution. If this is not provided, no refunds will be carried out

The asset will be registered with the metadata described in the summary. The setAssetUnitsPerSecond was calculated using the value for XRT value on November 8th 2022, targeting a XCM transaction cost of 0.02$.

If you are interested, the hex-encoded call data for this proposal in Moonriver is:


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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