Relevant smart contracts:

• ​CollateralAuctionHouse​

• ​DebtAuctionHouse​

• ​SurplusAuctionHouse​

1. Overview

The Auction Module is meant to incentivize external actors to drive the system back to a safe state by participating in collateral, debt and surplus auctions.

2. Component Descriptions

• The CollateralAuctionHouse is used to sell collateral from SAFEs that have become under-collateralized in order to preserve the overall health of the system. There are two flavours of collateral auctions: English and FixedDiscount.

  • The English auction version requires that bidders compete with increasing amounts of system coins for a fixed amount of collateral and only one bidder can win. This auction type has two phases: increaseBidSize where bidders submit higher system coin bids and decreaseSoldAmount where bidders accept a lower collateral amount for the winning system coin bid.

  • On the other hand, the FixedDiscount auction only has one phase (buyCollateral) where bidders submit system coins and the smart contract offers them collateral at a discounted price compared to its price. This auction type is more capital efficient and user friendly compared to English auctions. It also allows anyone to buy collateral using flashloans.

    By default, the contract will use the collateral's OSM price (which will lag compared to the actual collateral market price) and the system coin's redemptionPrice in order to calculate the amount of collateral to offer in exchange for each individual bid. On the other hand, governance can set the contract's parameters so that it uses the collateral's medianizer price and/or the system coin's market price if they deviated within certain limits from the OSM and the redemptionPrice.

• The DebtAuctionHouse is used to get rid of the AccountingEngine’s debt by auctioning off protocol tokens for a fixed amount of surplus (system coins). After the auction is settled, it sends the received surplus to the AccountingEngine in order to cancel out bad debt and it also mints protocol tokens for the winning bidder.

• The SurplusAuctionHouse (both its pre and post settlement versions) is used to get rid of the AccountingEngine’s surplus by auctioning off a fixed amount of internal system coins in exchange for protocol tokens. After auction settlement, the auction house burns the winning protocol token bid and sends internal system coins to the winning bidder.

3. Risks

Governance needs to fine-tune auction parameters in order to make the bidding process as efficient as possible. In the case of English, Debt and Surplus auctions there are three main parameters:

• bidIncrease- if it's too high it will discourage bidding and if it's too low its effect will be insignificant

• bidDuration- if it's too high it would force the winning bidder to wait too long until they can collect their winnings. If it's too low it would not give other bidders enough time to participate

• totalAuctionLength- if it's too high it would only delay auction settlement without any positive impact on the outcome. If it's too low it would make the auction settle before the true price is found.

• bidToMarketPriceRatio (only in English collateral auctions) - minimum mandatory size of the first bid compared to collateral price coming from the OSM

And in the case of FixedDiscount collateral auctions there's a wider range of variables:

• totalAuctionLength- same parameter as in the other auction types

• discount- discount applied to the collateral price

• minimumBid- minimum system coin bid that must be submitted by any bidder

• upperCollateralMedianDeviation- maximum upper side medianizer price deviation (compared to the OSM price) used by the auction contract to determine whether it will use the median or the OSM as a feed source

• lowerCollateralMedianDeviation- maximum lower side medianizer price deviation (compared to the OSM price) used by the auction contract to determine whether it will use the median or the OSM as a feed source

• lowerSystemCoinMedianDeviation - maximum lower side system coin market price (compared to the redemption price) used by the auction contract to determine whether it will use the market or the redemption price when determining the amount of collateral bought

• upperSystemCoinMedianDeviation - maximum upper side system coin market price (compared to the redemption price) used by the auction contract to determine whether it will use the market or the redemption price when determining the amount of collateral bought

• minSystemCoinMedianDeviation - minimum deviation between the market and the redemption prices of the system coin in order for the contract to choose the market price (and not the redemption one) when it determines the amount of collateral bought

4. Governance Minimization

Governance can completely remove control over all auction contracts.