Action Specification #

Action is a byte array which contains the data and instructions for the protocol to execute. In practice, the action is encoded in the transaction memo field, which is very limited in size. So the action should be as compact as possible.

To make the action compatible with URL encoding, we usually use base64 to encode the action.

MMISG #

MMISG is standard for "Mixin Milti-signature Group address". It's an address format to describe a multisig group or a single user in Mixin Network. It's supported by Pando's protocols and CoWallet.

A normal MMISG can be represented as following:

1     byte : version
1     byte : member_count
1     bytes: threshold
N     bytes: members

in which version is the version of the address, member_count is the number of members in the group, threshold is the threshold of the group, and members is the list of members’ uuids. Note that members should be always a multiple of 16.

In particular, if member_count is 1, then the address is a single user address, the threshold chould be omitted.

1     byte : version
1     byte : member_count (1)
16    bytes: member_uuid

If member_count is 0, then the address is a null address, the threshold and members should be omitted.

1     byte : version
1     byte : member_count (0)

Pando Action Protocol #

Each action chould be constructed as a header and a payload. The header is used to identify the protocol and the action, and the payload is the data of the action.

5~21  bytes: header
N     bytes: payload
4     bytes: checksum

Pando Action Protocol Header #

Protocol Header contains the version of the protocol, the protocol id, follow_id to trace it and the action.

It's used to identify the protocol and the action in the payload.

1     byte : version
1     byte : protocol_id
1     byte : has_follow_id or not.
16    bytes: follow_id, only if the previous byte = 1
2     bytes: action

In which,

• protocol_id is described in previous section.
• has_follow_id is a boolean value, if it's 1, then the follow_id is included in the header, otherwise it's not.
• follow_id is a 16 bytes uuid, it's used to trace the action. It can be omitted if the has_follow_id is 0.
• action is the action id. The meaning of the action id is described by the protocol.

Pando Action Protocol Checksum #

The checksum is used to verify the integrity of the action. It's calculated by the following formula:

checksum = sha256(sha256(header + payload))[:4]

Let's explain it in detail:

1. Concatenate the header and the payload.
2. Calculate the sha256 of the result.
3. Calculate the sha256 of the result again.
4. Take the first 4 bytes of the result.
5. The result is the checksum, append it to the end of the action.

SDK to generate action #

Although you can generate the action by yourself, and the action protocol is very simple, Pando Proto Team provides 2 packages to generate the action:

• Golang: pandodao/mtgpack
• Javascript: @foxone/memo-encode

Pando Action Protocol Payload #

The protocol body is attached to the protocol header. You can define the content according to your own needs

• 4swap
• Leaf