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Minting Process

The minting process at Tokentagged is not just about creating a token on the blockchain; it is the moment where the physical hardware is cryptographically and permanently bound to a specific Smart Contract Collection.

This process ensures that a Tokentag cannot be "re-used" for a different fake collection once it has been initialized.

Process Overview​

The minting workflow consists of three distinct phases that occur within a single user interaction (the "Tap"):

  1. Activation (if required): Deriving the wallet keys.
  2. Hardware Locking (NFC Write): Permanently storing the Collection Address on the chip.
  3. On-Chain Minting: Submitting the proof to the Ethereum Blockchain.

1. Activation Check​

Before minting, the Web App checks if the tag is already activated (i.e., has a derived private key). If not, the Trust Chain Activation is performed first.

To prevent a tag from being used to mint counterfeit NFTs on unauthorized contracts, the Tokentag hardware enforces a Write-Once policy for the contract association.

  1. Transmission: The Web App sends the address of the target Collection Smart Contract to the tag via NFC.
  2. Storage: The tag writes this address into a specific, protected memory sector.
  3. Locking: The tag permanently locks this memory sector. This action is irreversible.
Hardware Binding

Once a Tokentag receives a Collection Address, it is physically impossible to change it. The tag can no longer be used for other collections.

3. Cryptographic Signing​

The Web App requests a signature from the tag to authorize the minting transaction. The tag constructs a hash based on the current context and signs it with its unique Card Key.

The signed data includes:

  • Token ID: Derived from the tag's public key.
  • Operator: The wallet address of the user minting the item.
  • Collection Address: The address stored in the tag (ensuring the link).
  • Chain ID & Blockhash: For replay protection.

4. Smart Contract Execution​

The final step is the transaction on the Ethereum blockchain. The mintTokentag function in Tokentagged.sol orchestrates the validation and creation.

Function Signature​

function mintTokentag(
    uint256 tokenId, 
    string memory tokenURI, 
    uint256 amount, 
    address royaltyReceiver, 
    uint96 royaltyFraction, 
    uint blocknumber, 
    uint8 v, bytes32 r, bytes32 s, 
    bytes memory cardAttestation, 
    bytes memory attestation
)

Validation Logic​

The Smart Contract performs strict checks before minting:

  1. Signature Verification (_verifySignature):

    • Reconstructs the message hash using the contract's own address (address(this)).
    • Recovers the signer address using ecrecover.
    • Crucial Check: Validates that the recovered signer matches the tokenId (which contains the Tag ID). This proves the hardware authorized this specific contract.

  2. Attestation Verification (_authorizeTokentag):

    • Calls the SignerRegistry to verify the attestation and cardAttestation.
    • Ensures the chip is a genuine Tokentag manufactured by us.

  3. Supply Check:

    • Ensures the token hasn't been minted before (for NFTs).

Result​

If all checks pass, the token is minted to the user's wallet (_msgSender()), and the metadata URI is set. The physical object now has a verifiable digital twin.