> ## Documentation Index > Fetch the complete documentation index at: https://docs.ondo.finance/llms.txt > Use this file to discover all available pages before exploring further. # Smart Contract Reference > Smart contract interface for buying and selling Global Markets tokens with attestations. # IGMTokenManager The IGMTokenManager interface may be used by external parties to buy and sell Global Markets tokens using attestations. The general flow for each side is: **Buying GM Tokens** 1. User gets a signed quote (off‑chain) * The attestation service prepares a `Quote` whose side is `BUY`, signs its EIP‑712 digest, and returns the quote and signature to the user * Price is expressed in USD with 18 decimals (e.g., \$12.34 →12340000000000000000) * Quantity is the number of GM tokens the user wishes to receive 2. User pre‑authorizes USDon or USDC/USDT * GMTokenManager must have a sufficient allowance of USDon, USDC (Ethereum) or USDT (BNB Chain) before the call * Allowance ≥ price × quantity > 🚧 Notes on USDon > > * USDon will be Ondo's permissionless ERC20 stablecoin representing USD held in Ondo's brokerage account (which buys equities/ETFs backing GM tokens). Users can convert stablecoins to USDon with zero slippage by specifying it as the deposit token below. > * We accept USDC on Ethereum, and USDT on BNB Chain. > * If you would like to convert stablecoins to USDon *directly*, outside of a GM token swap, reach out to us and we can provide instructions for our USDonConverter contract. 3. User calls `mintWithAttestation(quote, signature, depositToken, depositTokenAmount)`, which will atomically: Verify the quote * Re‑computes the EIP‑712 digest and verifies the signature against the attestation signer * Confirm that the caller is whitelisted and their stored `userID` matches the one received in the quote * Ensures the `attestationId` has not been used and that `block.timestamp ≤ expiration` * Confirms side == `BUY` * Ensure the value of the transaction is greater than `minimumDepositUSD` but does not exceed per-user and per-token rate limits Settle the tokens * If the `depositToken` specified is not USDon, first swap `depositTokenAmount` for USDon * Burns price × quantity of USDon (either after receiving from `msg.sender` or swapping) * Mints quantity of GM tokens to `msg.sender` * Refund USDon to the user if any is leftover Post‑process the quote * Marks `attestationId` as consumed to prevent replay Return the tokens received * `receivedGmTokenAmount` equals quantity **Selling GM Tokens** 1. User gets a signed quote (off‑chain) * Attestation service issues a `Quote` whose side is `SELL`, signs it, and returns quote and signature * Price still uses 18‑decimal USD format * Quantity is the GM amount the user will sell 2. User pre‑authorizes GM tokens * GMTokenManager must have allowance ≥ quantity of the specific GM token (asset) described in the quote 3. User calls `redeemWithAttestation(quote, signature, receiveToken, minimumReceiveAmount)`, which will atomically: Verify the quote * Same as subscribe, but checks that side == `SELL` instead and that the transaction value is greater than `minimumRedemptiUSDon` Settle the tokens * Transfers quantity of GM tokens from user to manager and burns them * Mints out price × quantity of USDon to the GMTokenManager * If the caller specifies a non-USDon token as the receiveToken, it will swap all the USDon received for the receiveToken (note: the call will revert if the swap doesn't result in >= `minimumReceiveAmount` being received) * All tokens received are transferred to the caller Post‑process the quote * Marks `attestationId` as used Return the tokens received * `receivedUSDonAmount` equals price × quantity ## Functions ### mintWithAttestation Called by users to mint GM tokens with a quote attestation using either USDon, USDC on Ethereum, or USDT on Binance Smart Chain. *If the deposit token is not USDon and the depositTokenAmount is not enough to swap for USDon\ worth quantity \* price as specified in the quote, the transaction will fail as the `mintUSDonValue` is passed in to the minimum RWA received field in `subscribe`.* ```solidity theme={null} function mintWithAttestation( Quote calldata quote, bytes memory signature, address depositToken, uint256 depositTokenAmount ) public override whenMintingNotPaused(quote.asset) returns (uint256); ``` **Parameters** | Name | Type | Description | | -------------------- | --------- | --------------------------------------------------------------------------------------------------------------------------------------------------------- | | `quote` | `Quote` | The quote to mint GM tokens with | | `signature` | `bytes` | The signature of the quote attestation | | `depositToken` | `address` | The token the user would like to deposit in return for GM Tokens. If not USDon, this will be reliant on the ability to swap for USDon in the USDonManager | | `depositTokenAmount` | `uint256` | The amount of depositToken the user wishes to spend to purchase USDon atomically in the transaction | **Returns** | Name | Type | Description | | -------- | --------- | ------------------------------------------ | | `` | `uint256` | The amount of GM tokens minted to the user | ### redeemWithAttestation Called by users to redeem GM tokens for USDon. ```solidity theme={null} function redeemWithAttestation( Quote calldata quote, bytes memory signature, address receiveToken, uint256 minimumReceiveAmount ) public override whenRedeemNotPaused(quote.asset) returns (uint256); ``` **Parameters** | Name | Type | Description | | ---------------------- | --------- | -------------------------------------------------------------------------------------------------------------------------- | | `quote` | `Quote` | The quote to redeem GM tokens with | | `signature` | `bytes` | The signature of the quote attestation | | `receiveToken` | `address` | The token the user would like to receive. If it is not USDon, transaction success will depend on liquidity in USDonManager | | `minimumReceiveAmount` | `uint256` | The minimum amount of tokens the user would like to receive - ONLY applicable if the user requests a non-USDon otoken | **Returns** | Name | Type | Description | | -------- | --------- | -------------------------- | | `` | `uint256` | The amount of USDon minted | ## Structs ### Quote Quote struct that is signed by the attestation signer ```solidity theme={null} struct Quote { uint256 chainId; uint256 attestationId; bytes32 userId; address asset; uint256 price; uint256 quantity; uint256 expiration; QuoteSide side; bytes32 additionalData; } ``` **Properties** | Name | Type | Description | | ---------------- | ----------- | ------------------------------------------------------ | | `chainId` | `uint256` | The chain ID of the quote is intended for | | `attestationId` | `uint256` | The ID of the quote | | `userId` | `bytes32` | The user ID the quote is intended for | | `asset` | `address` | The address of the GM token being bought or sold | | `price` | `uint256` | The price of the GM token in USD with 18 decimals | | `quantity` | `uint256` | The quantity of GM tokens being bought or sold | | `expiration` | `uint256` | The expiration of the quote in seconds since the epoch | | `side` | `QuoteSide` | The direction of the quote (BUY or SELL) | | `additionalData` | `bytes32` | Any additional data that is needed for the quote | ## Enums ### QuoteSide Enum for the side of the quote ```solidity theme={null} enum QuoteSide { BUY, SELL } ``` # Contract addresses Contract addresses are available at the following page: [GM smart contract addresses](/addresses#ondo-global-markets).