Autentica ERC-721

Autentica Market (AUTMKT) is an ERC-721 smart contract that enables anyone to mint NFTs through our Marketplace. In addition to the ERC-721 standard, our smart contract also enables creators to receive royalties for each subsequent sale by implementing a proprietary solution which is described in the IERC721Autentica interface but also the ERC-2981 standard to ensure that creators are compensated for every sale, regardless of whether that sale occurs on the same platform where the NFT was originally created or on a different platform entirely that also supports that standard.

Minting NFTs can be a problem for many artists because of the technical aspects or because of the high costs associated to this process, and for this our Autentica Market (AUTMKT) smart contract enables creators that use our Marketplace to have someone else cover the minting process and pay for the gas fees associated to it. What this means is that a creator can choose to have an investor to mint the NFT on his behalf and also cover the associated gas fees, while the the newly created NFT is owned by the creator. This solution is implemented on both the Autentica Marketplace and the smart contract.

Technical details

The smart contract inherits OpenZeppelin Contracts's Context, ERC721URIStorage, ERC721Enumerable, and AccessControl abstract contracts and implements the IERC2981 and IERC721Autentica interfaces.

Types

In order to support royalties and keep references to the investors that handled the NFT minting process on behalf of other creators we defined the following structure called TokenDetails

struct TokenDetails {
    /// Address of the wallet that created the token.
    address creator;
    /// Address of the wallet who paid for gas fees.
    address investor;
    /// The value ranges between 0 and 100 multiplied by (10 ** DECIMALS).
    uint256 royaltyFee;
    /// The value ranges between 0 and 100 multiplied by (10 ** DECIMALS).
    uint256 investorFee;
}

This structure enables us to determine who created the token, who minted it (the creator or an investor), the royalty fee, and if the royalty fee should be shared with an investor if the token was not minted by the creator.

Storage

The additional storage that this smart contracts uses on top of the ERC721URIStorage, ERC721Enumerable and AccessControl is the address of the NFT Marketplace smart contract which handles the trading part and a mapping from token ID to the TokenDetails structure which contains information like the creator and investor address, royalty fee and the investor fee.

Operations

Minting

The standard minting process is to invoke the mint function with tokenId which represents a unique identifier for the NFT, uri which represents the Uniform Resource Identifier that identifies the JSON file describing the NFT, and royaltyFee which represents the royalties that the creator will earn from subsequent sales expressed as a percentage.

/**
 * @dev Creates a token for `_msgSender()`. The creator of the token and the owner of it will
 * be assigned to `_msgSender()`.
 *
 * @param tokenId Token ID.
 * @param uri Token URI.
 * @param royaltyFee Royalty fee.
 *
 * See {ERC721-_mint}.
 *
 * Requirements:
 *
 * - The `royaltyFee` must be less than or equal to 100 * (10 ** DECIMALS), meaning 100%.
 */
function mint(uint256 tokenId, string memory uri, uint256 royaltyFee) external

Investor Minting

If the creator is unable to mint the NFT due to the process's intricacy or the rising network gas fees, he/she can decide to mint the NFT through an investor. Prior to handing over the artwork to the Investor, he/she sets the royaltyFee that he/she wishes to earn from subsequent sales, as well as the investorFee, which represents the percentage that he/she gives to the Investor from his/hers proceeds each time the NFT is traded.

The investor then invokes the investorMintingAndApproveMarketplace function with the following parameters:

• creator which represents the address of the one that created the artwork

• tokenId which represents a unique identifier for the NFT

• uri which represents the Uniform Resource Identifier that identifies the JSON file describing the NFT

• royaltyFee which represents the royalties that the creator will earn from subsequent sales expressed as a percentage

• investorFee which represents a percentage from the creator's proceeds that is shared with the Investor each time the NFT is traded

• v, r and s that represents the ECDSA signature which verifies that the parameter values were chosen by the creator.

/**
 * Creates a token on behalf of a creator and approves the Autentica Marketplace smart contract.
 * The creator of the token and the owner of it will be assigned to `creator`
 * while the investor will be set to `_msgSender()`.
 *
 * @param creator Token creator and owner.
 * @param tokenId Token ID.
 * @param uri Token URI.
 * @param royaltyFee Royalty fee.
 * @param investorFee Investor fee.
 * @param v ECDSA `v` parameter.
 * @param r ECDSA `r` parameter.
 * @param s ECDSA `s` parameter.
 *
 * See {ERC721-_mint}.
 *
 * Requirements:
 *
 * - The `royaltyFee` must be less than or equal to 100 * (10 ** DECIMALS), meaning 100%.
 * - the `investorFee` must be less than or equal to 100 * (10 ** DECIMALS), meaning 100%.
 * - The investor can't be the creator.
 * - The ECDSA signature must be signed by someone with the admin or operator role.
 */
function investorMintingAndApproveMarketplace(
    address creator,
    uint256 tokenId,
    string memory uri,
    uint256 royaltyFee,
    uint256 investorFee,
    uint8 v,
    bytes32 r,
    bytes32 s
) external

Source Code

The source code for the token can be found in the AutenticaERC721.sol file located in the contracts folder within our smart-contracts repository.

Deployments

Network	Address
Ethereum	0x48a868dD45151800e306e83234c0EeF55E5BC624
Binance Smart Chain	0xf262a3b2a6973db844b6c82187d917e3b7a89170
Ethereum (Rinkeby)	0x7E7821ef6C1D635f4E7f9Bc0964207CB0F10F45f
Binance Smart Chain (testnet)	0x289a01be6A52B664D1C2EDEBB19F6C6419fb8229