TL:DR

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

Summary

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

• Multilocation: { "parents": 1, "interior": {"X1": { "Parachain": 2007}}}
• Decimals: 18
• Name: SDN
• Symbol: xcSDN

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

• Asset ID: 16797826370226091782818345603793389938
• XC-20 address: 0xffffffff0ca324c842330521525e7de111f38972

Proposal

Proposal #24 with the following hash: 0x1574f7ff82961dce53de55ae1c545ab3655105c40b16dba92fe03057028034e0

Technical details:

The procedure for opening the channels is as follows:

• Shiden: already proposed to open an HRMP channel to Moonriver
• Moonriver: democracy batched proposal:
  • Open Moonriver to Shiden HRMP channel
  • Accept Shiden to Moonriver HRMP channel
  • Register SDN asset as an XC-20
• Shiden: democracy proposal to accept Moonriver to Shiden 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 open the HRMP channel from Moonriver: hrmp.hrmpInitOpenChannel(recipient: 2007, proposedMaxCapacity: 1000, proposedMaxMessageSize: 102400), which its hex-encoded call data is 0x3c00d7070000e803000000900100
• To accept the HRMP channel to Moonriver: hrmp.hrmpAcceptOpenChannel(sender: 2007) , which hex-encoded call data is 0x3c01d7070000

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 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 SDN value on July 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:

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

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.