TL:DR

Similar to other HRPM channel proposals, we propose to Accept the HRMP channel between Bifrost (Kusama) and Moonriver.

Summary

We propose to accept the HRMP channel from Bifrost to Moonriver. Initially, the main use case will be to transfer BNC from Bifrost to Moonriver, but it can be further expanded to other use cases.
Due to current high block production times, the proposal has been fast-tracked.

Proposal

Referenda #77 with the following hash: 0xb9a83527d40a4d28321346eb73e9ad5431d3cc82d7330a12fab098324f750f96

Technical details:

To accept the HRMP channel, we need to execute the acceptance in Kusama. The related extrinsics are: hrmp.hrmpAcceptOpenChannel(sender: 2001), which its hex-encoded call data is 0x3c01d1070000.

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

The extrinsic 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

If you are interested, the hex-encoded call data for both the hrmpAcceptOpenChannel Moonriver is:

Accept Channel: 0x67000101000210000400000000070010a5d4e81300000000070010a5d4e8010700f2052a01060002286bee183c01d10700000d0100040001010070617261e7070000000000000000000000000000000000000000000000000000

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