use DOT/KSM/ROC as native parachain currency and allow down-/upward transfers

[brenzi]

DOT = the relay chain's native token, can be ROC, KSM too

scenario:

1. Start with zero DOTs on the parachain
2. send downward transfer X relay chain DOT to parachain
3. send tx on parachain, paying fees in DOT
4. send DOT back to relay chain (upward transfer)

resources

• https://wiki.polkadot.network/docs/en/build-parachains-rococo#how-to-make-cross-chain-transfers
• theory: https://w3f.github.io/parachain-implementers-guide/messaging.html

[brenzi]

This functionality seems not to be implemented for rococo-v1. We should wait until we have docs and examples from parity

[clangenb]

The current status for rococo-v1 is:

1. This is not wrapped in the polkadot-ui as it was for rococo-v0
2. Only available via sudo calls
3. A generic xcm message needs to be entered in a tedious manner.

[clangenb]

We decided to postpone this. There is a wip upward transfer pallet that wraps the generic xcm message in:

https://github.com/encointer/pallets/tree/pallet-xc-transfer-rococo

which has been integrated in: https://github.com/encointer/encointer-parachain/tree/native-dot-upward-and-downward-transfer

Current status: The xcm message is executed successfully. The balance is deducted from the sender, but it does not arrive at the relay chain.

[brenzi]

blocking upstream dependency:
paritytech/polkadot#2564

[brenzi]

@clangenb can you please check if PR#2995 enables us to resolve this issue?

paritytech/statemint might help as an example of how to use the relaychain native token as the parachain native token. It seems the process of upward/downward transfer of native tokens is now called teleport

We may want to wait until rococo-v1 supports this

[clangenb]

It does somewhat help us resolve this. Teleporting assets is currently limited to trusted teleporters, i.e. origins that are trusted to have irrevocably burned the assets in the origin system. These trusted teleporters are currently hard-coded in the runtime:

https://github.com/paritytech/polkadot/blob/master/runtime/rococo/src/lib.rs#L608-L613

[clangenb]

I have asked for the roadmap on the trust requirement in paritytech/polkadot#2564.

If there is no immediate plans for this, we could modify the rococo runtime and mark the encointer parachain as trusted.

[brenzi]

yes, do that plz! I suggest we don't wait as this issue is a strict necessity to be accepted as a common good parachain

[clangenb]

I believe we should wait after all, as the feature seems to be merged very soon, and it seems that the procedure for native up/-downward transfer is different for untrusted chains.

See: paritytech/polkadot#3010.

[brenzi]

that PR is included in 0.9.2
https://github.com/paritytech/polkadot/commits/v0.9.2

[brenzi]

@clangenb could we do this now based on polkadot 0.9.8?

[clangenb]

We should be able to do this. Note: polkadot-v0.9.9 is released already (at least in the Polkadot repository).

Because we are (most-likely) going to become a trusted common good parachain, the approach will be simplified compared to above. We can directly transfer funds with Teleportation instead of a ReserveAssetDeposit-XCM xt.