xDai $STAKE collab - Rainbow Bridge

nima · December 17, 2020, 10:58am

We’ve been having discussions here and there on Twitter about a potential collab/bridge between xDai and NEAR. Our friends from RaidGuild would 99% be interested in taking the lead on this one.

I would like to hear what everyone thinks about this and which strategic goals this collab should aim to achieve?

As far as I understand we have already made required changes to rainbow bridge to work with a PoA chain (vs. PoW), so xDai (PoS/PoA-ish) should be relatively easy!

Would love to hear thoughts/feedback from @alex.shevchenko @nearmax @illia and other folks involved in NEAR rainbow bridge … @sashahudzilin

Similar collab:

Twitter convos:

Pro:

Against-ish:

nima · December 17, 2020, 11:03am

Side note: @mattlockyer @mikedotexe is it feasible to use $ETH as gas (via Metamask) and some metatx magic to address @miohtama’s comment?

illia · December 18, 2020, 3:07pm

This offtopic for this, but our metatx inside EVM are designed to charge any token for gas. This can be wrapped ETH, DAI, etc.

nima · December 18, 2020, 5:03pm

Wow! That’s super cool do we have any documentation around this? Curious to read more!

illia · December 19, 2020, 4:12am

github.com/near/NEPs

Comment by ilblackdragon - Native EVM

near:master ← near:evm-precompile

Meta Transaction payments: We add an extra `(address feeTokenAddress, uint256… feeAmount)` parameter to meta message. This parameter tells protocol to charge this amount of given token from the signer of the message's account. Relayer decides if they want to relay such transaction based on the token address and amount -- e.g. if they want to accept payment in DAI or not. ``` fn meta_call(&mut self, args: Vec<u8>) { let { signature, fee_token_address, fee_amount, contract_id, args } = parse_args(args); sender = ecrecovery(hash(prepare_message(fee_token_id, fee_amount, contract_id, args)), signature); // calling ERC20(payment_token_id).transfer(relayer_id, amount) on behalf of the message signer. let {result, _} = interpreter::call(sender, fee_token_address, erc20_abi::encode::transfer(relayer_id, fee_amount)); if result == failure -> abort let {result, gas} = interpreter::call(sender, contract_id, args); let relayer_id = near_account_to_evm(self.predecessor_id); result } ``` Flow: - User indicates to frontend what action they want to execute and what token to pay with - Frontend queries relayers to get a "quote" on payment. Relayers can decide for themself on amount and if they want to support requested tokens - User signs a transaction that shows some amount of some token will be charged (or 0x0 if it’s free) - Any relayer can check again if they want to accept such message with given payment token/amount - Protocol executed the message and charges user, by transferring to the `predeccessor_id`'s address given amount. DApp specific relayers can decide to not charge anything, and accept `fee_token_address == 0x0`, which will pretty much waive the payment. Question: > Should user (frontend) specify the amount or should amount be inferred from the gas cost + gas amount inside EVM + some mark up to cover for external gas? Pros for specifying amount, is that relayer can charge whatever they want. User can decide to sign or not based on the cost. But this may lead to cost of relayer growing is the cost of the gas increased. Alternatively protocol (`near_evm_runner::EvmContext::meta_call`) knows the current gas costs that are paid and can charge the exact amount that was spent. Relayer paid extra fee. ### Concerns Relayer grieving - user signs a message that will pay 1 DAI to relayer to execute tx - relayer checks that user has 1 DAI - user transfers out 1 DAI away from account relayer sends the tx paying $NEAR for fee but tx fails because there is no DAI on users account I don't think it's a big issue, as user doesn't win anything and 1s blocks prevent doing this really easily as relayer may send their tx faster most of the times.

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xDai $STAKE collab - Rainbow Bridge

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