ICS100 Atomic Swap

[liangping]

Users may wish to exchange tokens without transfering tokens away from its native chain. ICS-100 enabled chains can facilitate atomic swaps between users and their tokens located on the different chains. This is useful for exchanges between specific users at specific prices, and opens opportunities for new application designs.

[AdityaSripal]

From a high-level this seems fine. It looks like the only time that the swap is locked in is after the TakeSwapPacket is successfully received. So there doesn't seem to be a way to have a one-sided transfer here. Though the transfer on the taking side might be delayed.

I have larger questions on how this might work for potential DeFi users. It seems like the maker has a free hand to cancel the order, after the take order is in-flight but before it gets received. Is this acceptable?

It would be helpful for someone with a Defi perspective to review this to see if it is making the right design decisions

[liangping]

First of all, thanks for the feedback!

I have larger questions on how this might work for potential DeFi users. It seems like the maker has a free hand to cancel the order, after the take order is in-flight but before it gets received. Is this acceptable?

This is a good question, Normally, Cancel Order has to cancel the order on the encounter-party chain first. then do it on itself. Therefore both Make Order and Cancel Order have long in-flight. It would be no problem if txs are executed in order, but seems it's no way to guarantee the executing order.

I believe either of following solutions will solve this issue.

• Remove cancel, the only way close the order is to fill the order on the encounter-party chain.
• Add timeout for Make Order, refund in a fixed time if it's not completed

What's your opinions?

[mpoke]

Thanks for the contribution @liangping. See my comments below, mostly related to improving the understanding of the protocol.

Regarding the high-level protocol, I do have the following concerns:

• Does the Maker module check when receiving a TakeSwap that the order_id is part of the OrderBook in the Taker module? Otherwise, the Maker could send a MakeSwap, and a malicious relayer could send back a TakeSwap followed by a Timeout (the MakeSwap is never received). As a result, the funds in the Maker module are both refunded and transferred to the Taker's address. Maybe the order should be saved on the Maker module onAcknowledgePacket.

• What happens if CancelSwap is received by the Taker module before the ACK for a previously sent TakeSwap?

[liangping]

@mpoke Sorry for delay. I missed your comments, hope this answer you questions.

• Does the Maker module check when receiving a TakeSwap that the order_id is part of the OrderBook in the Taker module? Otherwise, the Maker could send a MakeSwap, and a malicious relayer could send back a TakeSwap followed by a Timeout (the MakeSwap is never received). As a result, the funds in the Maker module are both refunded and transferred to the Taker's address. Maybe the order should be saved on the Maker module onAcknowledgePacket.

That's why we have two status on order, INITIAL or SYNC， INITIAL means just created. SYNC means taker chain confirmed(status updated onAcknowledgePacket). Now we use the hash of the packet as the order_id, which implies the port and channel on both chains

• What happens if CancelSwap is received by the Taker module before the ACK for a previously sent TakeSwap?

The order will be locked when takeSwap is sent, the cancel swap will be rejected when the order is locked. Only unlocked orders can be canceled.

[crodriguezvega]

Hi @liangping. If it's ok with you, I will push some changes on your branch for the code owners file and will add both you and @egunawan85 as owners of the spec to indicate that you will be the main maintainers. Please let me know if there's somebody else that I should add.

I will also add some text on the top of the spec to inform readers that the spec has been reviewed by the spec committee but will not be maintained by it.

[liangping]

@crodriguezvega I am ok. add egunawan85 and me to the owner for now. thanks

[mpoke]

LGTM

[AdityaSripal]

Hello @liangping please let me know if I can squash and merge

[liangping]

Hello @liangping please let me know if I can squash and merge

Yeah. Please!