Skip to main content

How to prepare Secret NFT assets

  • Off-Chain Metadata: Secret NFT metadata, Secret Media Metadata
  • Ternoa IPFS Client + one line helper: secretNftEncryptAndUploadFile - Encrypts and uploads a file on an IFPS gateway.

A Ternoa Secret NFT is composed of three files: a public asset file (e.g. image, video, music), a secret asset file (e.g. image, video, music) and a metadata json file. The asset file CID is nested into the metadata file and the three files are stored on IPFS (Interplanetary File Systems) with their dedicated hashes.

IPFS (Interplanetary File Systems) is one of the solution we recommend to upload NFTs medias and other associated metadatas. Thus offchain datas are stored in a fully decentralized way and only the link to this metadata is stored on-chain as part of the NFT. This link is frequently a fingerprint called a cryptographic ID (e.g. Qmf5RHhnUjSCfCN9d1Ee6sUWxe3Eqvogw1cTsssrxAxtPn). IPFS files are accessible using those hashes.

Ternoa provides its own IPFS public nodes on different HTTP gateways based on the network environement:

  • MAINNET: ipfs-mainnet.trnnfr.com
  • ALPHANET: ipfs-alphanet.trnnfr.com
info

Please note that an api-key is needed to store data on those gateways. Visit IPFS Keymanager to get your API Key.

Off-Chain Metadata​

An NFT is an unique ID. On-chain data contains this ID couple with additionnal important information like ownership, royalties and more. However medias and metadatas are stored off-chain for performance and flexibility. These data must be carefully written to guaranty a compatibility accross the tools and dApps of the ecosystem. Ternoa Improvement Proposals (TIPs) propose structures adopted from ERC-1155 to ensure this compatibility.

Here below is the expected format for secret NFT:

Secret NFT​

{
  "title": "(OPTIONAL) Title of the Secret NFT",
  "description": "(OPTIONAL) Description of the Secret NFT",
  "properties": {
    "encrypted_media": {
      "hash": "CID Hash of the encrypted media",
      "type": "Type of the encrypted media (file format)",
      "size": "Size of the encrypted media",
      "name": "(OPTIONAL) Name of the encrypted media",
      "description": "(OPTIONAL) Description of the encrypted media"
    },
    "public_key_of_nft": "Public key associated with the Secret NFT"
  }
}

Ternoa IPFS Client​

Prerequisites:

An IPFS client is available on Ternoa-JS SDK to make IPFS upload simple with only one line of code.

Place any asset you want to use at the root of your project and use this code snippet by completing FILE_NAME & FILE_TYPE:

import fs from "fs";
import { TernoaIPFS, File } from "ternoa-js";

const main = async () => {
  const file = new File(
    [await fs.promises.readFile("FILE_NAME")],
    "FILE_NAME",
    {
      type: "FILE_TYPE",
    }
  );

  const ipfsClient = new TernoaIPFS(new URL("IPFS_NODE_URL"), "IPFS_API_KEY");

  const nftMetadata = {
    title: "NFT TITLE",
    description: "NFT DESCRIPTION",
  };

  const { Hash } = await ipfsClient.storeNFT(file, nftMetadata);
  console.log("The off-chain metadata CID hash is ", Hash);
};

First the asset file is read from the file system and wrapped in a specific File instance imported from the Ternoa-JS library. The TernoaIPFS class is then used to create an IPFS client that connects to a specified IPFS node using a given API key. The metadata for the file is then defined in an object and passed to the storeNFT method of the client along with the File instance. The resulting Hash of the off-chain metadata is logged to the console.

The storeNFT method handles two IPFS uploads under the hood: a first one with the NFT media (e.g. the image) and a second one with the JSON metadata file, including the media's hash from the first upload response. This method also validates the metadata structure to ensure TIPs compatibility.

Next​

Next step will be the on-chain minting using Hash previously generated. Keep it and continue on the "How to mint a Secret NFT on-chain" guide.

Support​

If you face any trouble, feel free to reach out to our community engineers in our Discord.