## Explanation
There are many ways to get the signature signed by users. No matter which way NFT Data Chain will need the signature with a signed message, as shown below.
```yaml
# Message used to sign
nft_schema_code: # required
token_id: # optional, first one will be pick in case holder holds more than one
action:
timestamp: # the expired time in epoch format. NFT Data Chain will validate at the runtime whether the signed message is expired or not.
```
This is the protection to the users to ensure that no one can make a call on their behalf or use a signature on another action. But anyway, in this mode, the creator has complete control of the NFT, so the creator must verify this message by themselves.
### Creator Backend System
Cause in this mode, the creator has complete control of NFT Data. The creator needs to verify incoming data by themselves. Needed verifications are:
* Verify that the signer is the same as the NFT holder
* Verify that the metadata on NFT Data Chain is up to date with origin data
* Verify that action is correct
* Verify that signature is not expired.
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