Overview

FIP-27 has introduced the ability to use a FIO Handle to sign NFTs. An NFT is considered signed when the owner of the FIO Handle maps the NFT's contract address and token ID on specific chain to their FIO Handle. This acts as an attestation that they created the NFT. If the FIO Handle is known, for example an artist may publish their FIO Handle on their twitter account or website, then the attestation can act as a signature of the specific NFT.

For example, if an NFT has been signed and a user wants to know if their NFT is legitimate, they could verify the NFT signature by passing in the chain code, contract address, and token ID to the FIO Chain:

curl -s -XPOST https://fiotestnet.blockpane.com/v1/chain/get_nfts_contract -d '{
    "chain_code": "MATIC",
    "contract_address": "0xF5193f7c4312cA0759C91080e94E957F77669116",
    "token_id": "10"
}'

This returns "fio_address":"1969@woodstock thus verifying that the NFT was signed by the owner of the 1969@woodstock FIO Handle.

In addition, the artist can also append the hash of the asset (e.g. image, video, etc.) to ensure that the NFT points to the actual art work. This is important given that the files associated with the NFT are not always recorded on permanent and verifiable storage. For example, if the json for an NFT points to a generic URL for the image (e.g., http://shiftynfts.com/mynftimage.jpg) then there is a risk that the image of the NFT could get swapped out by a bad actor. In this case you may want to include the hash of your NFT in the signature. For example:

{
  "fio_address": "1969@woodstock",
  "nfts": [
    {
      "chain_code": "MATIC",
      "contract_address": "0xF5193f7c4312cA0759C91080e94E957F77669116",
      "token_id": "22",
      "url": "http://shiftynfts.com/mynftimage.jpg",
      "hash": "f83b5702557b1ee76d966c6bf92ae0d038cd176aaf36f86a18e2ab59e6aefa4c",
      "metadata": ""
    }
  ],
  "max_fee": 10000000000,
  "actor": "aftyershcu22",
  "tpid": "rewards@wallet"
}

This verifies that at the time this NFT was signed, the hash of mynftimage.jpg was f83b5702557b1ee76d966c6bf92ae0d038cd176aaf36f86a18e2ab59e6aefa4c. If another user acquires the NFT, they can get the hash of the image currently at http://shiftynfts.com/mynftimage.jpg and verify the signature:

curl -s -XPOST https://fiotestnet.blockpane.com/v1/chain/get_nfts_hash -d '{
    "hash": "f83b5702557b1ee76d966c6bf92ae0d038cd176aaf36f86a18e2ab59e6aefa4c"
}'

Native Integration

For wallets desiring full control over the registration user experience, the best strategy is to execute mapping actions directly to the FIO Chain.

Sign an NFT

To sign an NFT, use the addnft action and supply:

Sign All NFTs on a Contract

In certain cases you may want to sign every NFT (every Token ID) minted on a contract so it can be verified. This can be done by creating a "generic" contract-level signature where the token ID and other details of the NFT are not included. For example:

{
  "fio_address": "1969@woodstock",
  "nfts": [
    {
      "chain_code": "MATIC",
      "contract_address": "0xF5193f7c4312cA0759C91080e94E957F77669116",
      "token_id": "",
      "url": "",
      "hash": "",
      "metadata": ""
    }
  ],
  "max_fee": 10000000000,
  "actor": "aftyershcu22",
  "tpid": "rewards@wallet"
}

In this case, every token ID associated with this MATIC contract is considered signed by the 1969@woodstock FIO Handle.

Change NFT Signature Data

• To change chain_code, contract_address, or token_id, first remove the NFT using remnft, then add it back in using addnft.
• To change any other value, resubmit addnft action with new parameters.

Getters

Integrating these actions do not require the integrator to have access to user's FIO Private Key.

Available NFT Signature Getters

Write Transactions

Integrating these actions require the integrator to have access to user's Private key and properly serialize and sign each transaction. For additional information, see Write Transaction.

Available NFT Signature Actions

Link to FIO App

Alternatively to Native Integration, the application may link the user to to the FIO App, a comprehensive website to register and manage FIO Handles and many other functionality related to FIO Protocol.

For additional information, see FIO App.