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How to Mint NFT

tip

This is a guide for developers who want to mint NFTs for their users. For normal users, just use a Dapp like Trident to mint your NFT in a friendly web UI.

The typical steps to mint NFT on Mixin Network:

  1. Prepare metadata.json for your NFT
  2. Generate the metahash from metadata.json
  3. Upload metadata.json to Trident API
  4. Make the transfer to the NFO MTG

Metadata​

The NFO MTG doesn't maintain metadata for tokens, it's up to the token creators and token browsers to generate and verify the metadata according to the token hash.

Actually Trident will take the reponsibility to maintain metadata of NFTs for all token creators.

For the convenience to display NFTs in different token browsers, all metadata should follow the same format as following.

{
  "collection": {
    "id": "collection-uuid", // required
    "name": "collection name", // required
    "description": "description",
    "icon": {
      "hash": "hash of the collection icon",
      "url": "https url for the icon"
    }
  },
  "token": {
    "id": "token-identifier", // required
    "name": "token name", // required
    "description": "description",
    "icon": {
      "hash": "hash of the token icon",
      "url": "https url for the icon"
    },
    "media": {
      "hash": "hash of the token media",
      "url": "https url for the media",
      "mime": "the media mime type"
    }
  },
  "checksum": {
    "fields": ["collection.id", "collection.name", "token.id", "token.name", "token.media.hash"], // required
    "algorithm": "sha3-256", // required
  }
}

The basic infomation like collection.id, collection.name, token.id, token.name are required. Also the checksum field is required for verifying the interrelationship between the NFT and its metadata.

caution
  • collection.id must be a valid UUID string, which represents a collection, e.g. CryptoPunks. Everyone can start the collection if it is not minted yet.
  • token.id must be an integer, which is the unique identifier in the collection, e.g. 1234. Only the collection creator can mint a new token in it, while everyone can mint in the default collection.

Token creators may extend the format by adding more properties for any custom needs. Just make sure the metahash is generated from the specific content in checksum.fields using the checksum.algorithm.

tip

Any fields in the metadata.json may be added into the checksum.fields, which means they will be parts of the metahash and they cannot be modified once minted because they will be onchain data.

Metahash​

Mixin NFT's metahash is a 256-bit string generated from metadata.json using a particular algorithm, like sha3-256.

Let's take an example. Saying we have a metadata.json like this.

{
  "creator": {
    "id": "7ed9292d-7c95-4333-aa48-a8c640064186",
    "name": "李安"
  },
  "collection": {
    "id": "0ae66126-623b-47e4-a227-b54822b7498e",
    "name": "TRIDENT.TEST.AVATARS",
    "description": "Some cool avatars",
    "icon": {
      "url": "https://trident-test.onrender.com/rails/active_storage/blobs/proxy/eyJfcmFpbHMiOnsibWVzc2FnZSI6IkJBaEpJaWxoTkRSbU9UTTVOaTB4T0RRNUxUUTJOMlF0WWpVeU1TMDNOVGxoTnpjNE16VmtZVFlHT2daRlZBPT0iLCJleHAiOm51bGwsInB1ciI6ImJsb2JfaWQifX0=--e1d880c81d2fc893f85bd363ea31d86ea906656b/hdz7wp4jiq3szsizk2gqdabduesu"
    }
  },
  "token": {
    "id": "9879",
    "name": "A video sample",
    "description": "# A video sample\r\n\r\nshould play\r\n\r\nhash included",
    "icon": {
      "url": "https://trident-test.onrender.com/rails/active_storage/blobs/proxy/eyJfcmFpbHMiOnsibWVzc2FnZSI6IkJBaEpJaWxoTnpsa09HUXdOQzFpTUdGbUxUUTNZV010WVRFNVppMWtORGMxWlRnM05EWXhNRFFHT2daRlZBPT0iLCJleHAiOm51bGwsInB1ciI6ImJsb2JfaWQifX0=--76f65faef7654b8dc0afea79bb8d060b4991d83e/index.jpeg"
    },
    "media": {
      "url": "https://trident-test.onrender.com/rails/active_storage/blobs/proxy/eyJfcmFpbHMiOnsibWVzc2FnZSI6IkJBaEpJaWxoTVRFMU4yTmxPUzFrTm1WbUxUUmlZMlF0WW1FeE5DMDVZemRsTldZeE9UTTNNVFFHT2daRlZBPT0iLCJleHAiOm51bGwsInB1ciI6ImJsb2JfaWQifX0=--9bd0b779a7a1af74328d798aaabbb9b3f33f2e4d/file_example_MP4_640_3MG.mp4",
      "hash": "3c55ab75802f97411616668b5bbe1dee414565eb5f8b74c04d913113dde066b8"
    }
  },
  "checksum": {
    "fields": [
      "creator.id",
      "collection.id",
      "collection.name",
      "token.id",
      "token.name",
      "token.media.hash"
    ],
    "algorithm": "sha3-256"
  }
}

According to the checksum.fields, we use the specific 6 fields to generate the checksum content which will be

7ed9292d-7c95-4333-aa48-a8c6400641860ae66126-623b-47e4-a227-b54822b7498eTRIDENT.TEST.AVATARS9879A video sample3c55ab75802f97411616668b5bbe1dee414565eb5f8b74c04d913113dde066b8

Then we hash the checksum content string above using sha3-256 algorithm.

The result will be

8f31cb6b0a7f62294bc36864a5b8dff1fabe8cc9243bc7365a8c182e0a23eefa

So this is the metahash we need.

caution

If you want to add the media.hash to the metadata.json like the above example, make sure the hash is generated by the exact file specific in media.url using sha3-256 algorithm. Because Trident will verify that too when uploading metadata.

Upload Metadata​

Since we have metadata.json and metahash, we can upload them to the metadata maintainer Trident.

curl -X POST \
  'https://thetrident.one/api/collectibles?' \
  -H 'Authorization: Bearer eyJhbGciOiJFZERTQSIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2Mzk5OTY4OTUsImlhdCI6MTYzOTk5NjI5NSwianRpIjoiMDQxOGYxNmMtMGQ5Yy00MzVlLWIzY2YtYzg4MGZiZjUxYzA2Iiwic2NwIjoiRlVMTCIsInNpZCI6IjcxZjEzNGYzLTg2MTItNDQwNC1hYzI5LTc4NDg5NDlmNThkZiIsInNpZyI6IjVlNmI1OGZmYTEwYjNiYzUxNzI0ZmYwYmJkMmFmYjkxYzQ3NzFlZTM0MGY1ZDY4NTM0MGRmYTRjODU0YmFmYmEiLCJ1aWQiOiI2ZjlkYjBiYS00MDkxLTQzOWQtYjI4OC00YzFiZWU4MjUxYWMifQ.gFkhVRCeRbw6FbRTwJm1NyQcr192dki2B8EKROqDNAhYfpS-pv2kDtejyk_XJ8krak8aMltHgboSKG6IZHeQCA' \
  -H 'content-type: application/json' \
  -d '{
  "metadata": {"creator":{"id":"7ed9292d-7c95-4333-aa48-a8c640064186","name":"李安"},"collection":{"id":"0ae66126-623b-47e4-a227-b54822b7498e","name":"TRIDENT.TEST.AVATARS","description":"Some cool avatars","icon":{"url":"https://trident-test.onrender.com/rails/active_storage/blobs/proxy/eyJfcmFpbHMiOnsibWVzc2FnZSI6IkJBaEpJaWxoTkRSbU9UTTVOaTB4T0RRNUxUUTJOMlF0WWpVeU1TMDNOVGxoTnpjNE16VmtZVFlHT2daRlZBPT0iLCJleHAiOm51bGwsInB1ciI6ImJsb2JfaWQifX0=--e1d880c81d2fc893f85bd363ea31d86ea906656b/hdz7wp4jiq3szsizk2gqdabduesu"}},"token":{"id":"9879","name":"A video sample","description":"# A video sample\r\n\r\nshould play\r\n\r\nhash included","icon":{"url":"https://trident-test.onrender.com/rails/active_storage/blobs/proxy/eyJfcmFpbHMiOnsibWVzc2FnZSI6IkJBaEpJaWxoTnpsa09HUXdOQzFpTUdGbUxUUTNZV010WVRFNVppMWtORGMxWlRnM05EWXhNRFFHT2daRlZBPT0iLCJleHAiOm51bGwsInB1ciI6ImJsb2JfaWQifX0=--76f65faef7654b8dc0afea79bb8d060b4991d83e/index.jpeg"},"media":{"url":"https://trident-test.onrender.com/rails/active_storage/blobs/proxy/eyJfcmFpbHMiOnsibWVzc2FnZSI6IkJBaEpJaWxoTVRFMU4yTmxPUzFrTm1WbUxUUmlZMlF0WW1FeE5DMDVZemRsTldZeE9UTTNNVFFHT2daRlZBPT0iLCJleHAiOm51bGwsInB1ciI6ImJsb2JfaWQifX0=--9bd0b779a7a1af74328d798aaabbb9b3f33f2e4d/file_example_MP4_640_3MG.mp4","hash":"3c55ab75802f97411616668b5bbe1dee414565eb5f8b74c04d913113dde066b8"}},"checksum":{"fields":["creator.id","collection.id","collection.name","token.id","token.name","token.media.hash"],"algorithm":"sha3-256"}},
  "metahash": "8f31cb6b0a7f62294bc36864a5b8dff1fabe8cc9243bc7365a8c182e0a23eefa"
}'

Check the API for detail.

Transfer to NFO​

After the preparation above, we can do the actual minting: send 0.001 XIN to NFO MTG with a specific memo attached.

The memo can be created using the code below provided by nfo project.

nfo := nft.BuildMintNFO(collectionId, tokenId, metahash)
memo := base64.RawURLEncoding.EncodeToString(nfo)

Another choice to create memo is using the Ruby SDK.

MixinBot.api.nft_memo collection_id, token_id, metahash

The NFO MTG members are as below.

members = [
  "4b188942-9fb0-4b99-b4be-e741a06d1ebf",
  "dd655520-c919-4349-822f-af92fabdbdf4",
  "047061e6-496d-4c35-b06b-b0424a8a400d",
  "acf65344-c778-41ee-bacb-eb546bacfb9f",
  "a51006d0-146b-4b32-a2ce-7defbf0d7735",
  "cf4abd9c-2cfa-4b5a-b1bd-e2b61a83fabd",
  "50115496-7247-4e2c-857b-ec8680756bee",
]
threshold = 5

You may reference to transfer to a multi signature address or generate a payment to multisig address for user.

References​