## 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](https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Fwss.api.moonriver.moonbeam.network#/extrinsics/decode) 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.

 Add a registrar to the system.

 The dispatch origin for this call must be `T::RegistrarOrigin`.

 - `account`: the account of the registrar.

 Emits `RegistrarAdded` if successful.

 # <weight>
 - `O(R)` where `R` registrar-count (governance-bounded and code-bounded).
 - One storage mutation (codec `O(R)`).
 - One event.
 # </weight>

- Problem Statement: The proposal aims to accept the HRMP channel between Bifrost (Kusama) and Moonriver.
- Significance: The proposal will allow for the transfer of BNC from Bifrost to Moonriver and can be expanded for other use cases.
- Proposed Solution: Execute the acceptance of the HRMP channel in Kusama using specific extrinsics and call data.
- Expected Outcomes: Successful acceptance of the HRMP channel, enabling the transfer of assets between Bifrost and Moonriver.

#77 Accept HRMP Channel from Bifrost to Moonriver