# Protocol Spec

#### MetaID Protocol Specification

The MetaID protocol is structured as follows:

```jsx
<metaid_flag> 
<operation> 
<path> 
<encryption> 
<version>  
<content-type> 
<payload> 
```

The MetaID protocol consists of seven parts:

#### **\<metaid\_flag>**

A fixed value "metaid" used as the protocol identifier.

This is a required field.

#### **\<operation>**

Operation commands, supporting four types of commands:

* **`create`**: Creates content, creating a PIN at the specified path.
* **`modify`**: Modifies content, modifying the PIN at the specified path.
* **`revoke`**: Revokes content, declaring the PIN at the specified path as void.
* **`hide`**: Creates and hides a PIN. After using this command, no PINNumber will be assigned.

This is a required field.

#### **\<path>**

The path where the PIN is located. There are three modes for indicating the path:

* Starting with “/”, the path locates the PIN to be created, such as /protocols/simplebuzz.
* Starting with “#”, the path locates the PIN by PINNumber.
* Starting with “@”, the path locates the PIN by PINID.

This is a required field.

#### **\<encryption>**

The encryption method for the PIN content. 0 means no encryption; 1 means ECIES encryption; 2 means ECDH encryption.

This is an optional field. If not provided, it must use `OP_0` as a placeholder, with a default value of `0`.

#### **\<version>**

The version number of the PIN. Different version numbers may imply different formats for the payload content.

This is an optional field. If not provided, it must use `OP_0` as a placeholder, with a default value of `0`.

#### **\<content-type>**

Specifies the file format of the `payload`, including the encoding method of the `payload`.

All media types can be referenced from: <https://www.iana.org/assignments/media-types/media-types.xhtml>

This is an optional field. If not provided, it must use `OP_0` as a placeholder, with a default value of `application/json`.

#### **\<payload>**

The `payload` is arbitrary data content, with its format specified by \<content-type>. The MetaID protocol does not limit the length of the `payload`. It is only constrained by the size of a single transaction data on the blockchain where the PIN is located.

This is an optional field. If not provided, it must use `OP_0` as a placeholder.


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