There are Three types of Stable Coins, but we will be only discussing two major ones.
Before we move forward I strongly recommend reading my post on “How Stock prices are decided”
Fiat-Collateralized Stablecoins (The Centralized Model)
A fiat-collateralized stablecoin is a simple digital IOU (I Owe You). It is a token that represents a claim on one real US dollar held in a real, traditional bank account.
The Operator: A central, trusted company (like Circle for USDC or Tether for USDT) is the issuer.
The Promise: For every 1 USDC token that exists on the blockchain, the company (Circle) promises that it is holding 1 real US dollar in its audited bank reserves.
The Mechanism: The company acts as a bridge between the traditional banking system (TradFi) and the blockchain world (DeFi).
How They Work - The Minting and Redemption Process
The 1:1 peg is maintained by a simple, direct, two-way process: minting (creation) and redemption (destruction).
The Minting Process (Real Dollars -> Crypto Dollars):
The User: A large financial institution or trading desk (let's call them "Big Trader Inc.") wants to get $10 million of USDC to use in DeFi.
The Wire Transfer: Big Trader Inc. sends a $10 million wire transfer from their traditional bank account to the stablecoin issuer's (Circle's) bank account.
The Verification: Circle's internal systems see the $10 million arrive. They now have the real-world collateral.
The Mint: Circle's authorized system then calls the mint() function on the official USDC smart contract on Ethereum. They mint 10,000,000 new USDC tokens directly to Big Trader Inc.'s crypto wallet address.
The Result: The total supply of USDC has increased by 10 million, and this is 100% backed by the 10 million real dollars that were just added to the reserves.
The Redemption Process (Crypto Dollars -> Real Dollars):
The User: Big Trader Inc. has finished its DeFi operations and now wants its real dollars back. It has 10,000,000 USDC in its crypto wallet.
The "Burn" Request: They send the 10,000,000 USDC back to a special "burner" address controlled by Circle. The smart contract removes these tokens from the total supply.
The Verification: Circle's systems see that the tokens have been verifiably burned on the blockchain.
The Wire Transfer: Circle then initiates a $10 million wire transfer from its bank reserves back to Big Trader Inc.'s traditional bank account.
The Result: The total supply of USDC has decreased by 10 million, and the corresponding 10 million dollars have been removed from the reserves and sent back to the user.
How the Peg is Maintained
The mint/redeem mechanism creates a powerful arbitrage opportunity that keeps the price on the open market locked to $1.00.
If the price of USDC on a DEX drops to $0.99: Arbitrageurs will buy up the cheap USDC on the open market, redeem it with Circle for $1.00 of real cash, and pocket the 1-cent profit. This buying pressure pushes the price back up to $1.00.
If the price of USDC on a DEX rises to $1.01: Arbitrageurs will wire $1.00 to Circle to mint 1 new USDC, then sell that USDC on the open market for $1.01, pocketing the 1-cent profit. This selling pressure pushes the price back down to $1.00.
This constant arbitrage ensures the peg remains extremely tight.
The "Trust" Component - Strengths and Weaknesses
Strengths:
Simplicity and Stability: This model is very easy to understand and has proven to be extremely robust at maintaining its peg.
Capital Efficiency: It is 1:1 backed. There is no need for the complex over-collateralization we see in other DeFi protocols.
Weaknesses (The Centralization Risk):
Counterparty Risk: You must trust the central company (e.g., Circle). You have to trust that they actually have the reserves they claim to have. This requires relying on traditional, third-party auditors.
Censorship Risk: The company that controls the smart contract has the power to freeze funds or blacklist addresses. They can be compelled by law enforcement to do so. If your address is blacklisted, you can no longer send or receive USDC. This violates the core "permissionless" ethos of DeFi.
The whole concept of Decentralization is broken here, you have to depend on a centralized currency to make decentralization possible
Crypto-Collateralized Stablecoins (The Decentralized Model - MakerDAO & DAI)
Instead of backing a stablecoin with dollars in a bank, you back it by locking up volatile crypto assets (like ETH) in a smart contract. But this immediately creates two massive questions, which will form the structure of our lesson:
The Collateral Problem: How can you back a stable asset with a volatile asset? What happens when the price of the collateral (ETH) crashes?
The Peg Problem: How do you keep the price of this new token, DAI, at exactly $1.00 if there's no central company to redeem it for real dollars?
Let's begin with the first question.
The Collateral Mechanism - "Vaults"
This part will feel familiar, as it uses the same core principle as the lending protocols we studied: over-collateralization.
The Process of Creating (Minting) DAI:
The User (Alice): Alice has ETH but needs liquidity (stablecoins). Instead of going to Aave to borrow pre-existing DAI, she goes to the MakerDAO protocol to create brand new DAI.
Opening a Vault: Alice interacts with the MakerDAO smart contract system to open a "Vault" (sometimes called a Collateralized Debt Position or CDP). A Vault is a smart contract that will hold her collateral.
Depositing Collateral: Alice deposits 10 ETH (currently worth $20,000) into her Vault. This ETH is now locked by the MakerDAO protocol.
Minting DAI: The protocol has a Minimum Collateralization Ratio for each asset. For ETH, let's say it's 150%. This means for every $1 of DAI she creates, there must be at least $1.50 worth of ETH locked in her Vault.
Maximum DAI she can mint = Value of Collateral / Minimum Ratio
Maximum DAI = $20,000 / 1.5 = ~13,333 DAI.
Alice Stays Safe: To avoid being instantly liquidated, Alice decides to be conservative. She mints only 10,000 DAI against her $20,000 of ETH.
The Result: 10,000 new DAI tokens have just been created. They are sent to Alice's wallet. Alice now has a debt of 10,000 DAI to the MakerDAO protocol, and her 10 ETH is locked as collateral against this debt. Her Vault's current collateralization ratio is $20,000 / 10,000 = 200%, which is safely above the 150% minimum.
Common Doubt #1: "Isn't this just borrowing? How is it different from Aave?" This is a brilliant question. The mechanics are very similar, but the purpose and origin of the asset are completely different.
In Aave (Lending): You borrow DAI that already exists and was supplied by another user (Dan the Lender). You are a participant in a two-sided credit market.
In MakerDAO (Minting): You are the one creating the DAI. It did not exist before you locked your collateral. You are not borrowing from another person; you are minting a new currency against your own assets. MakerDAO is a central bank, not a peer-to-peer lending market.
Repaying the Debt and Reclaiming Collateral: To get her ETH back, Alice must repay the 10,000 DAI she minted, plus a small "stability fee" (the interest rate). When she sends the DAI back to her Vault:
The DAI is burned (permanently destroyed).
Her debt is cleared.
The protocol unlocks her 10 ETH, which she can then withdraw.
Solving the Collateral Problem - Liquidation
This works exactly like in a lending protocol, but it's even more critical here because it's the only thing that ensures every single DAI in circulation is sufficiently backed.
The Scenario: The price of ETH drops to $1,500.
Alice's Vault:
Collateral Value = 10 ETH * $1,500 = $15,000.
Debt = 10,000 DAI.
Current Collateralization Ratio = $15,000 / 10,000 = 150%.
The Danger Zone: Her Vault is now at the absolute minimum ratio. If the price of ETH drops any further, her Vault will be liquidated.
The Liquidation Process: The MakerDAO protocol will seize her 10 ETH collateral. It then sells off just enough of the ETH in an automated, on-chain auction to raise the 10,000 DAI needed to pay back her debt. The remaining ETH (minus a penalty fee) is returned to Alice.
The Result: The 10,000 DAI debt has been eliminated from the system, and the 10,000 DAI tokens that depend on it are now considered fully backed again. The system remains solvent.
Common Doubt #2: "What if the ETH price crashes so fast that even after seizing the collateral, it's worth less than the debt?" This is the "black swan" event that the system must handle. If the auction for the liquidated ETH fails to raise enough DAI to cover the debt (creating "bad debt"), the protocol has a backup plan. It will trigger a "Debt Auction." In this event, the protocol mints a small amount of its governance token, MKR, and sells it on the open market to raise the DAI needed to cover the shortfall. This dilutes the value of MKR, giving all MKR holders a strong incentive to govern the system well and set risk parameters (like the 150% ratio) conservatively to avoid this scenario.
The Peg Problem - How DAI Stays at $1.00
This is the most complex and beautiful part of the system. We've established how DAI is backed, but not why it trades at $1.00. The peg is maintained through a delicate balance of economic incentives for arbitrageurs, controlled by two main policy levers that the MakerDAO community can adjust.
Lever 1: The Stability Fee (The "Interest Rate" on Minting DAI)
What it is: The interest rate that Vault owners (like Alice) must pay on their DAI debt.
How it affects the peg:
If DAI is trading above $1.00 (e.g., $1.01): This means there is high demand for DAI and not enough supply. The MakerDAO governance can lower the Stability Fee. This makes it cheaper for people like Alice to mint new DAI. More people will lock up ETH to mint DAI and sell it on the market for $1.01, pocketing a profit. This increases the supply of DAI, pushing its price back down to $1.00.
If DAI is trading below $1.00 (e.g., $0.99): This means there is too much DAI in supply and not enough demand. The MakerDAO governance can raise the Stability Fee. This makes it more expensive to hold a DAI debt. It incentivizes people like Alice to go to the open market, buy up the cheap $0.99 DAI, and use it to pay back their debt and stop paying the high interest rate. This decreases the supply of DAI, pushing its price back up to $1.00.
Lever 2: The DAI Savings Rate (DSR)
What it is: A smart contract that allows any DAI holder to deposit their DAI and earn a stable interest rate, paid for out of the Stability Fees collected from borrowers.
How it affects the peg:
If DAI is trading above $1.00: The DSR is less relevant, as the primary incentive is to mint new DAI.
If DAI is trading below $1.00: The MakerDAO governance can raise the DAI Savings Rate. This creates a high-yield savings account for DAI. It incentivizes traders to buy up the cheap $0.99 DAI on the market and lock it in the DSR to earn this attractive, risk-free yield. This increases demand for DAI, pushing its price back up to $1.00.
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