#7 Referendum proposal: Accept HRMP channel request from Karura


HRMP (Horizontally Relay-routed Message Passing) is a stop-gap that predates XCMP. Semantically, it copies XCMP’s interface. The crucial difference from XCMP though is that all the messages are stored in the relay-chain storage. The HRMP will be expected to retire once the XCMP is available.

Opening of HRMP channel between Bifrost and Karura will initially release the cross-chain communication between two parachains:

  • Tokens on both sides can be transferred to each other.
  • Messages can be received on both sides, calling functions by each other.


  • :raising_hand_man: Voting Period: #488,880
  • :rocket: Activate Period: #489,180
  • Encoded call: 0x3c01d0070000
  • Sender: 2000
  • Proposal preimage: 0x4a00010000040a00070010a5d4e808070100ca9a3b00000000005ed0b2000000000004060000ca9a3b00000000183c01d007000001040101020070617261d1070000000000000000000000000000000000000000000000000000
  • Proposal hash: 0x5b8dd1125205a0b4dc6c1ea8b76bbac6f0b6b6333c13fafd7ab07c4ce936fbfe

This withdraws 1 KSM to buy transaction fee, execute the call to accept open channel request, and refund remaining KSM to the parachain sovereign account eGJrytyJYDzMGM1uji4Bx5ntw3xF6aifJ7Xvo3mE48cgW5N

Two proposals are required on Karura and Bifrost to establish a bidirectional HRMP channel.
The whole flow will be roughly like this:

  1. Initiate requests
    a. Karura’s proposal to request to open Karura to Bifrost HRMP channel
    b. Bifrost’s proposal to request to open Bifrost to Karura HRMP channel
  2. Wait until proposals on step 1 are approved & enacted
  3. Accept requests
    a. Karura’s proposal to accept Bifrost to Karura HRMP channel
    b. Bifrost’s proposal to accept Karura to Bifrost HRMP channel
  4. Wait until proposals on step 3 are approved & enacted
  5. Wait for another session on Kusama for the change to be effective
  6. Cross-chain transfer BNC will be possible at this stage. Other kinds of cross-chain interaction such as transfer of KAR & kUSD will be enabled at a later stage via runtime upgrade of Karura & Bifrost.

As mentioned above, #6 referendum proposal, the current HRMP opening process has reached stage 3.b, this proposal will accept a request from Karura to open the HRMP channel. After the channel is opened, this will be the first time in history of two parachains communication with XCM in the production environment. Let us witness history together!


Totally agreed. XCMP transactions will be awesome!

Aye again and again !!