Background
DEX is planned to be implemented as Iroha 2.0 module.
Action items
- Nikita Puzankovwrite down scenarios
- Yuriy Vinogradov validate scenarios
- Egor Ivkov Vladislav Markushin provide implementation options
- 武宮誠 review solution
Problem
Decentralized exchange provides an ability to transfer assets between accounts in exchange for other assets. Let's use a simple case as an example:
Peer to Peer Scenario
So Iroha should secure peer to peer exchanges across the ledger from malicious actions. In this case Iroha does a good job, the only thing it should check is an ability to transfer assets from and to accounts.
But there are more corner cases when we deal with exchanges via bridge:
Peer to Peer across Bridge Scenario
- Cross blockchain rates should be taken into consideration
- Iroha should prevent double spent of assets
- Additionally to transferring assets, Iroha should mint and de-mint them
Simple scenario:
Liquidity Pool Scenario
Liquidity Pools is another dimension in this set of scenarios for Decentralized Exchanges. Basically it can be used in pair with or without bridges, so let's take a more clean example without them. But let's not stick to an Exchange Pair and work with multi-currency liquidity:
From the high level perspective this scenario looks very similar with two previous because all of them are based on top of two Iroha functions:
- Assets Transfer
- Iroha Triggers
Resulting Behavior
Let's write all three scenarios as one feature description according to BDD with more details:
Feature: Decentralized Exchange Scenario: Buyer exchanges 20xor for 100usd Given Iroha Peer is up And Iroha DEX module enabled And Peer has Domain with name exchange And Peer has Account with name buyer and domain exchange And Peer has Account with name seller and domain exchange And Peer has Asset Definition with name xor and domain exchange And Peer has Asset Definition with name usd and domain exchange And buyer Account in domain exchange has 100 amount of Asset with definition usd in domain exchange And seller Account in domain exchange has 20 amount of Asset with definition xor in domain exchange When buyer Account places Exchange Order 20xor for 100usd And seller Account places Exchange Order 100usd for 20 xor Then Iroha transfer 20 amount of Asset with definition xor in domain exchange from seller account in domain exchange to buyer account in domain exchange And Iroha transfer 100 amount of Asset with definition usd in domain exchange from account buyer in domain exchange to seller account in domain exchange Scenario: Buyer exchanges 1btc for 20eth across bridges Given Iroha Peer is up And Iroha Bridge module enabled And Iroha DEX module enabled And Peer has Domain with name exchange And Peer has Account with name buyer and domain exchange And Peer has Account with name seller and domain exchange And Peer has Asset Definition with name btc and domain exchange And Peer has Asset Definition with name eth and domain exchange And Peer has Bridge with name btc and owner btc_owner And Peer has Bridge with name eth and owner eth_owner And eth Brdige has buyer Account in domain exchange registered And btc Brdige has seller Account in domain exchange registered When buyer Account places Exchange Order 20xor for 100usd And seller Account places Exchange Order 100usd for 20 xor Then Iroha mint 1 amount of Asset with definition btc in domain exchange to seller Account in domain exchange using btc Bridge And Iroha mint 20 amount of Asset with definition eth in domain exchange to buyer Account in domain exchange using eth Bridge And Iroha transfer 1 amount of Asset with definition btc in domain exchange from seller account in domain exchange to buyer account in domain exchange And Iroha transfer 20 amount of Asset with definition eth in domain exchange from buyer account in domain exchange to seller account in domain exchange Scenario: Buyer exchanges 20xor for 100usd Given Iroha Peer is up And Iroha DEX module enabled And Peer has Domain with name exchange And Peer has Account with name trader and domain exchange And Peer has Account with name seller and domain exchange And Peer has Asset Definition with name xor and domain exchange And Peer has Asset Definition with name btc and domain exchange And Peer has Asset Definition with name eth and domain exchange And trader Account in domain exchange has 1 amount of Asset with definition btc in domain exchange And trader Account in domain exchange has 20 amount of Asset with definition eth in domain exchange And trader Account in domain exchange has 20 amount of Asset with definition xor in domain exchange And seller Account in domain exchange has 20 amount of Asset with definition eth in domain exchange When trader Account registers Exchange Liquidity 20xor and 20eth and 1btc And seller Account places Exchange Order 20eth for 1btc Then Iroha transfer 1 amount of Asset with definition btc in domain exchange from seller account in domain exchange to trader account in domain exchange And Iroha transfer 20 amount of Asset with definition eth in domain exchange from trader account in domain exchange to seller account in domain exchange
Solution
Introduce a new module "DEX" with a dependency on "Bridge" module with additional set of Iroha Special Instructions and Queries and new Abstractions like Order (Combination of a Trigger and Asset with a predefined Asset Definition). Implement Triggers.