Minting and Redeeming

Minting

All XUSD tokens are fungible with one another and entitled to the same proportion of collateral no matter what collateral ratio they were minted at. This system of equations describes the minting function of the XUSD Protocol:

F=YPycollateral value+ZPzXUS value(1Cr)(YPy)=Cr(ZPz)F = \overbrace{Y * P_y}^\text{collateral value} + \overbrace{Z * P_z}^\text{XUS value} \\ (1 - C_r)(Y * P_y) = C_r(Z * P_z) \\

FF is the units of newly minted XUSD CrC_ris the collateral ratio YY is the units of collateral transferred to the system PyP_yis the price in USD of YYcollateral ZZ is the units of XUS burned PzP_zis the price in USD of XUS

Example A: Minting XUSD at a collateral ratio of 100% with 200 DAI ($1/DAI price)

To be explicit, we can start by finding the XUS needed to mint XUSD with 200 DAI ($1/DAI) at a collateral ratio of 1.00

(11.00)(1001.00)=1.00(ZPz)0=(ZPz)(1−1.00) * (100∗1.00) =1.00 * (Z∗Pz) \\ 0 = (Z * P_z)

Thus, we show that no XUS is needed to mint XUSD when the protocol collateral ratio is 100% (fully collateralized). Next, we solve for how much XUSD we will get with the 200 DAI.

F=(2001.00)+(0)F=200F=(200∗1.00)+(0) \\ ​F=200

200 XUSD are minted in this scenario. Notice how the entire value of XUSD is in dollar value of the collateral when the ratio is at 100%. Any amount of XUS attempting to be burned to mint XUSD is returned to the user because the second part of the equation cancels to 0 regardless of the value of ZZ and PzP_z.

Example B: Minting XUSD at a collateral ratio of 80% with 120 DAI ($1/DAI price) and an XUS price of $2/XUS.

First, we need to figure out how much XUS we need to match the corresponding amount of DAI.

(10.8)(1201.00)=0.8(Z2.00)Z=15(1−0.8)(120∗1.00)=0.8(Z∗2.00) \\ Z = 15

Thus, we need to deposit 15 XUS alongside 120 DAI at these conditions. Next, we compute how much XUSD we will get.

F=(1201.00)+(152.00)F=150F=(120∗1.00)+(15∗2.00) \\ F = 150

150 XUSD are minted in this scenario. 120 XUSD are backed by the value of DAI as collateral while the remaining 30 XUSD are not backed by anything. Instead, XUS is burned and removed from circulation proportional to the value of minted algorithmic XUSD.

Example C: Minting XUSD at a collateral ratio of 50% with 220 DAI ($.9995/DAI price) and an XUS price of $3.50/XUS

First, we start off by finding the XUS needed.

(1.50)(220.9995)=.50(Z3.50)Z=62.54(1−.50)(220∗.9995)=.50(Z∗3.50) \\ Z = 62.54

Next, we compute how much XUSD we will get.

F=(220.9995)+(62.543.50)F=437.78F = (220*.9995) + (62.54*3.50) \\ ​F=437.78

437.78 XUSD are minted in this scenario. Proportionally, half of the newly minted XUSD are backed by the value of USDC as collateral while the remaining 50% of XUSD are not backed by anything. 62.54 XUS is burned and removed from circulation, half the value of the newly minted XUSD. Notice that the price of the collateral affects how many XUSD can be minted – XUSD is pegged to 1 USD, not 1 unit of DAI.

If not enough XUS is put into the minting function alongside the collateral, the transaction will fail with a subtraction underflow error.

Redeeming

Redeeming XUSD is done by rearranging the previous system of equations for simplicity, and solving for the units of collateral,YYY, and the units of XUS,ZZZ.

Y=F(Cr)PyZ=F(1Cr)PzY=\frac{F∗(C_r)}{P_y} \\ ​Z=\frac{F∗(1−Cr)}{Pz}

FF is the units of XUSD redeemed CrC_ris the collateral ratio YYis the units of collateral transferred to the user PyP_y​is the price in USD of YYcollateral ZZ is the units of XUS minted to the user PzP_zis the price in USD of XUS

Example D: Redeeming 170 XUSD at a collateral ratio of 65%. Oracle price is $1.00/DAI and $3.75/XUS.

Y=170(.65)1.00Z=170(.35)3.75Y=\frac{170∗(.65)}{1.00} \\ ​Z=\frac{170∗(.35)}{3.75}

Thus, Y=110.5Y = 110.5and Z=15.867Z = 15.867

Redeeming 170 XUSD returns $170 of value to the redeemer in 110.5 DAI from the collateral pool and 15.867 of newly minted XUS tokens at the current XUS market price.

NOTE: These examples do not account for the minting and redemption fee, which are set to 0.7% and 0.3% at launch